I love your in depth floppy disk vids Rob, they so interesting and technical with great graphic illustrations, thanks for taking time to do these for us disk nerds:)
that little tagline on the thumbnail "Only amiga makes it Possible" unlocked a damn earworm outta my early years hearing that music video on the same name "Only Amiga"
Long time Amiga owner from the US and I have never heard of DiskSpare!!! Really interesting... At 984K, that's right up there with the amount Randy Linden was able to get on a disk for Dragon's Lair. As I understand it (from MVG), that was 1040k per disk. I always thought that was incredible black magic, but to think there there was a magazine using a format that got almost that much is incredible!!!! Great vid!!!
@@RobSmithDev - There was a similar floppy disk method on the C64 achieving incredible read speeds. Write was still slow but the read was 10x or more faster with some gap tricks. I think it was called Express or Jet Load.
Most of the reasons for not putting more on the disks were due to reliability issues. The Disk drives,heads and physical media all added up to issues if you tried to store too much onto it. 720kb (for PC) was a safe standard for everything.
Interesting stuff indeed, I typically formatted disks on the ST at 820K (82 tracks 10 sectors) as I found 11 sectors to not be 100% reliable a lot of the time.
These tricks remind me of a pair of programs for the PC, FDFORMAT and its TSR support program, FDREAD. They allowed you to do some tricks such as reducing the number of root directory entries to a single sector (which, perhaps surprisingly, was compatible without having to use FDREAD) and adding sectors to each track and adding 2 extra tracks (82 tracks instead of 80). Using such tricks, a 1.44MB HD floppy disk could store something like 1.76MB (I'm not sure of the last digit). But if you wanted to store a single file which was just a little too large for a floppy disk, reducing the number of root directory entries was a useful trick which meant that the disk was still usable in any MSDOS machine without needing a support program.
ב''ה, if you're interested in this, OS/2 XDF is a hazy memory and a source of significant headaches, but IBM was trying to squeeze room out when Warp (3.0) still came on floppies as well.
FAT12 and FAT16 Boot Records have an field that specifies the number of (8.3) root directory entries. The value in this field will determine the root directory size. The "normal" number of root directory entries is 512. Since each entry occupies 32 bytes the "normal" root directory will occupy 16384 bytes or 32 sectors. Dropping the number of root directory entries to 16 will give you 31 more sectors for data without confusing DOS.
@@josephkanowitz6875 PC DOS 7 was also distributed on floppies using the XDF format. The XDF TSR allowed DOS to use a floppy with this format. The XDFCOPY utility is included for duplicating XDF formatted floppies.
@@oledave2540 That's exactly what I found in my investigations. If you change the boot record to say that there are only enough root directory entries for a single sector, then the root directory will only occupy that single sector, leaving the rest available to be used as storage. It was just right if you only needed a tiny bit more space and you were storing only a few files, using the root directory only.
I think this is the first time I see this YT channel, and I'm positively surprised with accuracy of ST's tidbits. Been playing around with floppies back in the day (ST 3.5/5.25/SD/DD/HD, synchro express, 800's 1050/551, etc.), and watching this was a nice flashback.
Oh there were so many ways to format floppy disks! :-) Not just what personal and home computers did but also other hardware that used them. Early PC disk maintenance programs could do things like interleave the sectors which often gave a significant speed boost. And then there were formats with varying sector sizes. I believe the Ensoniq Mirage did this, giving the sampler just a little bit more savable storage.
I remember, it was pretty common in 90's to format HD disks with 20 sectors per track and 82 tracks, obtaining even 1.6MB capacity. And it was completly not a big deal to format a DD disk to 10 sectors per track (800KB). I'm talking about PCs.
The Amiga floppy interface was flexible because it was quite dumb and simple - the Paula disk logic was basically a shift register and FIFO buffer sitting between the floppy drive data lines and the DMA engine. The status and control signals were connected to I/O pins on the CIA chips, relegating all the drive control tasks to software. Even the MFM decoding and encoding was done by the software (some loaders used the blitter for this). (Yes, there were a few extra features I didn't get into, such as wordsync)
Regarding labels, yes I remember that - my basic theory, a previously re-used "recycled" disk was likely cheaper than a brand new disk, and at a certain point towards the end of software being supplied on floppy disk likely a massive collection of surplus/spare double density disks previously duplicated and labelled for predominantly PC software ended up being returned, and possibly because PCs moved quickly towards high density disks a certain amount ended up being repurposed as Amiga magazine coverdisks. P.S. disk re-use also happened with PC format coverdisks too.
That brings back memories! I remember using that file system as a means of backing up my hard disk. The backup program also compressed the data, so attempting to use as few floppies as I could get away with!
Disc duplicators would always use new discs because they were more reliable, however sometimes they didn't. What would happen is that there were shortages that sometimes occurred. It's not a shortage in that floppies became scarce on the shelves, but in bulk purchases. When duplicators bought discs they bought by the thousands at an extremely low price. When they couldn't buy at that low price they went to disc reclaimers who were supposed to clean the labels and blank the discs (at one place I knew of they would literally hose off the discs with just tap water then scrape off the labels and then run big magnets over them and lastly hang them up with a fan (those were the super cheap discs! no returns). But sometime when deadlines were crazy shortcuts were taken and you get a huge box of all different discs with whatever was on them "good luck"
Nice one! Tracks and sectors constantly remind me of XCopy 2d grid (8 rows by 10 columns + unused 9th row that can only have 2 columns - guess that'd be some extra for the DiskSpare?), or "formatting cyl 0 of 79" formatting disks in AmigaDos. Lol at the "that's what FFS stands for, not what you're thinking!" 😆
Sounds like some of the tricks Apple did on the classic macs. (the outer tracks had more sectors) And the Microsoft "distribution" format pushing the DOS/Windows install discs to 1.68MB. (written track-at-a-time with no sector gap)
I loved DiskSpare! Got 1.96MB per disk with my high density floppy drive. BTW the 837K for OFS was, the actual usable storage space VS the 720K "PC" disk which was the theoretical max including the filesystem overhead. Really, the PC had far less than 720K actually usable space. I seem to recall the FFS came out prior to KICKSTART 2.O.
Actually, Atari ST formatted disks could be read on DOS-PCs directly, if these were formatted either with TOS 1.04 upwards, or a 3rd party formatter like Hyperformat. Only TOS 1.0 and 1.02’s formatting routines had a bug that prevented DOS recognizing the disks from the ST. As you mentioned, the other way round (PC->ST) was never an issue. The 1st program on the ST to go beyond 880KB was Hyperformat from Claus Brod and Anton Stepper. TIL that the Amiga went far beyond 900KB! Its "full track" tricks can’t be done on the ST, as this one uses a "classic" floppy controller WD1772 that works per sector.
How Floppy disks actually work always makes my head spin. The multiformat disks always seem like magic to me. A disk that can be read on the Amiga, Atari ST and DOS!
@@RobSmithDev I have a bunch of them that came with an Atari ST I picked up in a charity shop over twenty years ago. The floppy drive had been replaced and was upside down if I remember rightly. I only booted it up a couple of times because upside down disc drive was a bit unreliable and it's sat in a cupboard since then. I've ripped the discs as I was curious to have a tinker but the flux images have also just sat barely looked at.
Cool stuff Rob. I had not heard of that format as, being from Canada, I had subscriptions to AmigaWorld and Amazing Computing, and the only UK magazine I regularly bought was Amiga Format. I do recall AUI but for some reason it just didn't appeal to me. I recently built a DrawBridge using a spare Arduino and have been having fun with that. Thanks for all the cool stuff you are doing with these great old machines. Any chance you will be attending this year's World of Commodore show in Toronto? 😄
Some Amiga magazines published an occasional dual format disk that mixed in ST formatted tracks in areas that weren't strictly required by the Amiga OFS. Also, FFS was available for hard drives, but I'm not sure if it did similar low level trickery as with floppies. I remember it being perceivably faster with caveats - pre-2.0 Kickstart ROMs could not boot FFS partitions although these could be mounted after booting off of an OFS partition, and, there were people who backronymized FFS for what you actually WOULD think because they had their FFS partitions get repeatedly corrupted. I remember there was some software for the PC that could also, with some disk controllers at least, write a "huge" extra amount of data on DD and HD disks... also I managed to buy some cheap disks of questionable quality that were not very good at the standard HD format, but when I configured a standard 3,5'' HD drive as a 1,2MB 5,12'' drive in the setup as my B drive, it would happily use that (almost) 1,2MB per disk without issues, while in 1,44MB format those same disks would have so many bad sectors that the usable space went way below 1MB. It is possible that these were actual old DD rusts packed in HD shells and wished Bon Voyage. This seemingly goes to show that the disk rusts had a rather sharp limit of frequency they could reliably record, and lowering the recording frequency only by approx. 17% made them work way better.
I’ve got a video coming up on the dual format disks - they’re interesting in their own way. Not all hard drives allowed you to change anything to do with sectors - some were ‘hard sectored’ and those were the ones that if you low level formatted them couldn’t be used again. It doesn’t surprise me that some (later) pc controllers had more control over the disk
This reminds me that I remember xcopy by default didn't copy past 79. I sometimes wondered if games that didn't work after a copy was because I never added those extra sectors.
xcopy didn't actually have anything to do with it. You could load the dos floppy.sys driver and give it the right arguments to access a floppy with different geometry, but most people didn't, and so floppy access was left up to the PC BIOS ( int 13h ), which normally had a small menu that let you tell it that you either had a 720k or 1.44 MB 3.5" floppy, or a 5.25" floppy . If you told it you had a 1.44 MB 3.5" floppy, it assumed 18 sectors per track and 80 tracks.
@@phillipsusi1791 He means the Amiga software named X-Copy... a different animal. This was a track-to-track disk copy program that had some extra tricks up its sleeve as well, namely copying disks with non-native encoding. It could at least theoretically duplicate any disk that didn't exceed 82 tracks or didn't require using a higher frequency to record a track than what was used for the 11 sectors. I remember attending one of the early Assembly parties, I had my trusty old Amiga there... ended up discussing the different disk shenanigans with a PC user, and showed them that not only I can duplicate the DD disk we were given to store our votes, but I could mount the disk for file access, and even run some of the simpler PC programs in the PC emulator.
@@jussikuusela7345 Ahh, I remember playing games on Amigas in an Amiga store next to the landrymat where my mom worked after school, the the kids of the people who ran the Amiga store. DOS also had an xcopy command that was just a better file copy command, so I thought that is what was being talked about. I'm not familiar with the amiga one. It sounds like you are talking about something more like the unix dd utility that just read and wrote each sector on the disk without regard for the filesystem.
With Atari st the max was with most of dd drives was 83 tracks and 11 sectors, 913 kb / 934 912 bytes formatted so that the formatted disk was accessible without any extra utilities.
I discovered Diskpare on an Aminet CD that i purchased in the 90s. I used it on my A1200 it was brilliant being able to store all my music modules and instruments disks. I think i did and test with 10 of my most used disks and managed to cut the 10 down to 7 disks. Shame it couldn't be used to increase the size of my 60Mb hdd inside the A1200.
Slight variance in speed would only be a problem if writing to the floppy, it would overrun and corrupt the first sector. I suspect most cover disks didn't write to the original media. ST allows whole track read or write but the problem with track write is that some values are reserved as commands to create gaps etc so is less versatile than the Amiga there.
i remember having a HD floppy (1.7mb?) on my A1200 tower. i think it was just a slowed down DD, but i might be wrong. It would be good to get a similar deep dive into that. I think A4000 had a HD floppy? good vids for us fellow nerds
Yeah the HD drives just span the disk at half the speed so could fit twice as much, there’s not really that much more to it other than some signalling that went on to tell the Amiga it’s an HD disk.
I have a (now broken) Amiga copy of Utopia where the disks were old copies of an Atari game Federation of Free Trade, printed directly on the disk, but the Utopia label was just stuck on top of it. I think when they needed some stock of one game, they'd just take whatever disks they had from unsold stock and just write on top of them.
Do you know how MacroSystem did this on the DraCo with their DraCo format floppies? They stored around 900kb on a floppy, twice that for HD floppies. DraCo can read/write regular Amiga formats as well. And has Amiga DOS drivers so your Amiga can read DraCo formatted floppies.
One thing that's worth considering is that I used extended formats to squeeze almost 1MB out of my disks on the Atari ST. However, 30 years on those disks are completely unreadable, I imagine it was a combination of imperfect storing conditions, cheap media (poor student) and pushing the media past its specifications. I was a sad man when I lost all my code from those years. I really should have copied the data to a hard disk or something when I first started getting into PCs
Storage of disks in a dry environment was important. I have loads of disks from that time period that work perfectly but I was just lucky. Sadly though like you, I have a few that are beyond their life
I still have my 1.76.MB Drive on my A500+ which can be format to nearly 2.MB. In have 3 external floppy drives in total which were put to good use on games that were on many floppies.
very interesting! talking about atari st and amiga disk formats, i had a flashback... and now a request: could you also make an explainer about the "argonaut dual loading system" used with the starglider 2 game?
I always used 1.7M HD Discs back in the days on my PC formatted with VGACOPY. If I remember right it goes up to track 82, but I think sectors didn't change or I can't remember.
I had quite a few with labels underneath but I don't think they were second hand. I can only imagine towards the end they were using whatever disks they could find at the cheapest price and that must have included (unused) discs that had prior software on them.
software publishers would send the unsold software to get recycled.. they would magnetically erase the disks and bulk pack them for software distribution publications like the aol mailer and magazines.
I wonder how much they could have packed if they started using variable drives like the commodore floppy drive used to. EG there were four zones from the inside track to the outside tracks. If I remember correctly they varied the bitrate. That's why they can put more sectors on per track as they went to the outer tracks. The reason was fairly simple there was more track length on the outer tracks versus the inner. So it wouldn't overwhelm the the media's ability to distinguish between the bits on the track
I suspect the extra complexity involved is why they didn’t - and would have needed a specially made drive I guess. A bit like the earlier Apple drives. But yes then much more data.
The limit was never really the physical medium. It was the ability of the electronics to operate at higher bit rates, which they would have to do in order to do that.
Great video as always Rob, Never heard of diskspare before today. that would have been super helpful back in the day too! Great to hear flashback is getting an update. Wondering if there's any plans / way to add apple support to it? I've been using my drawbridge floppy for all sorts lately but apple disks caught me out lately.
All but the first 2 or 3 floppy disks that Windows NT 3.50 came on also used that 1680 KB format. I started using Linux around that time and managed to get 1920 KB on a floppy using a mixed sector size format.
3.5" DSDD disks were advertised as 1MB unformatted and DSHD, 2MB. The actual size was obviously determined by the various platforms and filesystems as per Rob's coverage here. Question Rob, how did you produce the graphical representation of what the disk surface looked like?
Huh? DSDD 3.5" disks were advertised as 1.44 MB, because they held 18 sectors per track and 80 tracks per side, for 1440KB. Then they came out with those high density drives at 2.88 MB but floppies became obsolete before I ever got one of those.
There’s a program called HxD floppy emulator that will do this from disk images. I changed the colour scheme to suite me. It’s a handy tool for checking backups etc are ok
@@phillipsusi1791 Unformatted VS formatted. Formatting uses some of the theoretical space for sector indexing etc. You could write a proprietary code to store as much data on a disk as the controller, drive mechanism precision, and disk rust quality allow, but that would at worst be very touch and go with any other drive and controller than the combination you wrote it for. Instead the standard PC formatting uses a recording frequency that is in a fairly well proven range, and inserts indexing data and padding that are not seen as user data... Amiga uses a slightly higher frequency and arranges that padding and indexing in a different way, allowing approximately 22% more storage on the same rust, actually getting fairly close to the theoretical 1 or 2 MB unformatted specification.
@@jussikuusela7345 You can't really talk about the capacity of an unformatted disk, therefore, all of the capacities I have been speaking of are for formatted disks. The standard PC format used 18 512 byte sectors per track, times 80 tracks, times 2 sides, to store 1440 KiB. There was a Linux tool called superformat that could instead format the disk to use, I think it was only two sectors per track, one that was 16 KiB and one that was 8 KiB to store a total of 1920 KiB, by reducing the overhead of the sector headers. You could not control the raw bit rate or rotation rate of the drive, all you could do was change the sector size and try to find a combination that the drive could manage to write to the track before the first bit came back around again. I feel like you may be confusing the two different kinds of formatting. People used to speak of a "formatted" disk as one that you ran the DOS format command on, which would write a FAT12 filesystem to the disk. The filesystem of course, has some of its own overhead to keep track of what clusters belong to what file, and store the names of the files, but that is very different from the low level format, which laid out what sectors existed in what position on the disk.
@@phillipsusi1791 Actually, 1440KB was HD and 720KB was DD. Fun fact - Double Density disks were used with MFM encoding, which could encode twice the number of bits compared to the earlier FM. Because the MFM scheme always had at least one 0 between two 1 bits, you could double the number of bit cells in a track while maintaining the same flux reversal density - essentially squeezing an extra bit cell between two flux reversals.
So it is kind of like Shingled magnetic recording (SMR) in some hard drives. Can you try this trick on 1.44 HD and wishful thinking 2.88 ED Disks. Only wish that 2.88MB disk became popular in the day.
:) unlike a lot of people my entry to the Amiga was the A500+ so I started with Ks2.04, DriveID - how the Os discoverers what type of disk is inserted is interesting though
@@RobSmithDev A500+512 Expansion back in 1988 then the good old A2000. Mind just boggles how it knows. And having just bought a modded PC drive to read HDDs just shows how much wasted potential there was.
I don't exactly remember if it was PFS or SFS or what other name but I'm pretty sure I've been using some filesystem that let me write over 1MB on one DD disk. I think it was actually a question of settings in the filesystem settings file where you can set the block size or something like that.
Yes changing the block size would help - but this is close to the physical limits of the disk. I doubt it was PFS or SFS as they were mainly used on hard drives but I know there was another one and I don’t remember its name
@@RobSmithDev There was AFS (AmiFileSafe) which i recall getting from a cu amiga coverdisk. it later became PFS I believe or it was the floppy part of it.
Thanks for reminding us of AFS and PFS. Yes as l recall they did work on floppy drive. Atomic Commit included. I seem to recall PFS allowed even longer filenames.
The drive speed wasn't critical, there's a phase locked loop to cater for different speeds. So long the speed was mostly constant. Ie a clicky floppy disk slows down rotation for and instant. Still in many cases the disk could still be read if the controller can adapt quickly enough. If drive controllers could vary the flux transition lengths more could be stored on disk until you hit the magneting density limit. Higher frequency pulses loose their signal strength quicker. Varying pulse length per track would've been possible though.
Same with what they did on the LS240 using standard floppies, because the more precise (but lot more expensive...) drive could simply "pack more". That is, assuming your magnetic substrate wasn't total dos**t like it was the case for "no name brands" of the day...
This is true a, but machines like the Amiga couldn’t - they had a fixed clock for writing so couldn’t ‘cheat’ like that. The drive speed is Important, sure for reading there’s the PLL, but writing, well it literally can affect how much space there is
I had a program on the PC that formatted a disk to 1.9MB instead of 1.44MB. No idea anymore what it was called, probably came from a shareware CD. Or a magazine.
No I wasn’t. I made Drawbridge and the Floppy Bridge plugin for WinUAE as well as DiskFlashback so I’ve had to understand a lot about low level flux stuff to make all that work.back in the day I only ventured as far as Amos
@@RobSmithDev well your videos are absolutely amazing and a treat to watch! And I never even had an Amiga back in the day (386sx-25 home PC user). Keep up the fantastic work bud and have a great week!
i wonder why they didn't go to 1024bytes sectors, as it was common on PCs. or even different sector sizes per track. so you could minimize the total number of gaps per track.
@@phillipsusi1791 Standard, but this video is about "super density formats". 828kB on 2DS floppies was a widly used format on PCs. but this was not the limit, when making disks for drives with better tolerances.
Thing is, the file systems typically can’t store more than 1 file per sector so the larger the sector size the less number of files you can fit - so it’s a little bit of a trade off
I was a fond user of DS till i found an other Filessystem wich name i dont remember anymore ... I was able ot fit over 1.0xx KB on a Standart DD Disk... Sadly its been way to long to remember. While i always formated the DiskSpare Devices with DS0 the other one was maybe called FS0 ? gosh its been a while.. but blew my mind!
Aha! I wasn't imagining it! I've been trying to remember the name of that one too. As far as I recall, it could squeeze about 1.2Mb on a DD floppy. The size sticks in my mind because I remember thinking how ridiculously close it was to the capacity of a high density PC disk. It wasn't as robust as DiskSpare, though. Despite its trickery, that was rock-solid. [EDIT: I think I've found it. I'll post a new comment.]
@@VividNation Strange. I can't see it now myself. I definitely posted one. Anyway, I realised that I'm still using my old disk image from back in the day with UAE, so I had a look around it. There's an FS0 DOSDriver, and a “floppy.device” in DEVS. I'm sure that's it. I *think* it was called Floppy Filesystem.
I never had any problems with DiskSpare. There was another one that could fit even more data on the disk. 1.1 mb rings a bell, but I can't remember what it was called.
Oh I use to buy boxes of disks from a company calling themselves 'Chickenshit Software' and pretty much all their disks were recycled old versions of PC software, thier labels were so sticky it was near impossible to get them off but a hot water bottle would soften the glue enough to let you carefully peel it to reveal the original contents, if it was interesting then you could usually 'unformat' the disk.
Wasn't there also a trick where you altered the disk read process. I think shadow of the beast used this to cram onto disk far more data than was normally possible
It was probably using long tracks if it needed to store extra data. Has to be written using an external device as the Amiga can’t write them, but can read them.
Have you tried sticking one of your custom floppies into a stock Acorn Archimedes, running RISC OS 3.1 (1990), or later, as notionally capable of reading, in addition to Acorns own 100 / 200 / 400 / 640 / 800 / 1600 KB DFS / ADFS floppy formats (SS SD, DS SD, DS DD, DS DD, DS HD), assorted Atari ST, and IBM PC FAT floppies. Not sure about the Watford Electronics and Solidisk disk formats, that those companies sold ROMs advertising more space per disk than Acorn, for the BBC micro. You also missed the Mitsumi QuickDisk system, that used a spiral track, and appeared on the MSX, Roland synthesisers, ...
Hehe I didn’t ‘miss’ any other formats because the video wasn’t about that. It makes sense though that the Archmides could do a better job, it was a later system so was probably designed more flexible/do it in software rather than hardware
The Amiga 4000 supported HD disks, formatted in its own and FAT formats. While the QuickDisk systems, sold for some MSX, Nintendo, Roland, Spectrum, ... didn't use sectors, just end of file markers.
Wrong, the original ones could, I used it in an XT exact-clone. Also 2M would replace the BIOS allowing to use 3.5 drives in old computers (HD ones required replacing the controller, DD ones didnt). They had two formats, 2M changed the number of bytes per sector (but same for the whole track) and the number of sectors per track. While 2MGUI also used different sector sizes in the same track. Kryoflux was unable to read 2MGUI of any kind a few years ago 😂. Thing is the Amiga could do this trick even easier as they could use any encoding (2M was limited by the 765 derivates), as was done to read Apple’s GCR, so I always supposed someone did that, playing with Paula?
fascinating. I guess, there is no way to slow down the disk during reading and writing in the outer sectors. otherwise, you could squeeze 1,5mb on such a disk.
@@RobSmithDevPlatform wars are childish and pointless which makes them a stupid thing to engage in. I never understood them even back in the day - it was so obvious the Amiga was & still is the vastly superior platform you'd have to be literally blind to not be able to see that.
@@RobSmithDev youtube provides automatic captioning and this works quite good since years. sure, they are not flawless, but much better than nothing. that's automatically active usually. so you turned it off apparently.
If you want a good understanding of some more formats (why the apple ][ only had 144kb a disk for example on the 5.25in disks) then there's some nice manuals from the copy protection programs out there. I had book of 3 or 4 manuals together at one point. I think it was locksmith, Nibbles away and another manual. Really informative about disk formatting and concepts like track arching and so on. 2M on the IBM PC is one of the best resources for high density floppies on that system. I think 2m source code exists out there somewhere?. Teledisk/Anadisk are also fantastic low level formatting/copying programs for the IBM PC and you can learn a lot about formatting etc. You can make stupid high density disks on ibm like 20mb but if you move/tap or breath on the disk it just breaks. It's possible to "store" data on it but it's highly unreliable.
I recall a utility I had for PC that would format a floppy to more than 720k and it was usable in dos. Some of my disks are formatted with it and I can’t read them in windows 😂 (or they might just be bad 🤣)
If they didn't use the standard format, you had to load a driver to access them in DOS. Windows is going to be expecting the standard format, so if it isn't that, it can't read it. The Linux floppy driver had a bunch of different /dev/fdXXXXX devices for non standard formats and if you used the right one that corresponded to the format of the disk, you could access it.
Yes you’re losing your mind 😂 that’s the capacity of a PC High Density disk. The Amiga could fit 1.76MB on those and if you used DiskSpare you could get upto 1.9MB! - but not many people were lucky enough to have a high density drive on the Amiga
@@RobSmithDevI had one of the dell external floppy drives that were sold with an Amiga cable. I'm not sure how many of them were sold, I think it was just a batch of drives that someone found in a warehouse. At the time they came out, there was no reason why you would need a half speed floppy drive on a pc.
Huh? wasn't 720k single density? Double density was 1.44 MB. I remember using superformat in my early Linux days to cram 1920 KB on those by using mixed sector sizes. Microsoft did something similar to fit more data onto the ~40 floppy disks or so that Windows NT 3.50 came on. The first 2-3 disks had the standard 1.44 MB format so they could load the drivers to access the extra capacity on the rest. You could get extra capacity on floppies in DOS by loading the floppy.sys driver with the right arguments too. And I also did format some disks with 82 tracks. I sometimes had trouble reading them back through on computers other than the one that formatted the disk. When I was in college, an open source Windows NT clone called ReactOS came out and I contributed to that for a while. Including writing the floppy disk driver. I was very confused as to why the driver worked fine in the bochs PC emulator, but not on real hardware. It turned out that while the floppy controller specifications said there was a command to probe the geometry of the drive, no actual hardware ever actually implemented it, which is why PC bios always had a screen where you had to TELL it the type of drive you had connected, and both the Windows and Linux drivers just used the geometry the bios said to rather than try to probe it.
@@MurrayDagostino Wait, so there were FOUR generations of 3.5" floppies? I only remember three: 720k, 1.44M and 2.88M if you even count that last one. Before that I remember 1.2MB and 600k 5.25" drives. I only ever remember PC BIOS having the choices between 720k and 1.44M for 3.5" drives and 600k/1.2MB for 5.25".
So that is how DiskSpare worked: I AM DISAPPOINT! I thought it was a whole lot cleverer than that, using alternative MFM encodings. If you have stared at MFM bitstreams then you have seen that there are legitimate bit combinations that will never be generated by the standard encoding method. To try to use that you would have to build a bitstream much like arithmetic encoding where you can never know what the data represents before you have decoded everything coming before it. The possible size savings seem non-deterministic and depends on your data - you might want to try strategies to massage it to get a more favourable position.
I guess there’s two reasons why this isn’t done. The first is it would make the encoding and decoding far too complicated for the electronics of the time - or at least, too expensive. The other is if you were using a standard floppy disk drive then you have to be careful with the minimum and maximum time between flux transitions. I’ve explained how at a low level this works in a much earlier video. Plus those ‘not normally encoded sequences’ are useful to trigger things (eg sector start sync words)
@@RobSmithDev I am talking about 100% in-spec MFM standard, but it needs to be software en/de-coded (well, nothing says you can't make hw for it, but on the Amiga you only have the raw data anyway). There is a long thread on EAB where we discussed it.
I love your in depth floppy disk vids Rob, they so interesting and technical with great graphic illustrations, thanks for taking time to do these for us disk nerds:)
that little tagline on the thumbnail "Only amiga makes it Possible" unlocked a damn earworm outta my early years hearing that music video on the same name "Only Amiga"
😂😂
Long time Amiga owner from the US and I have never heard of DiskSpare!!!
Really interesting...
At 984K, that's right up there with the amount Randy Linden was able to get on a disk for Dragon's Lair. As I understand it (from MVG), that was 1040k per disk.
I always thought that was incredible black magic, but to think there there was a magazine using a format that got almost that much is incredible!!!!
Great vid!!!
Thank you. I did manage to squeeze just over 1M onto the disk myself and I could read it back but sadly the Amiga couldn’t - was fun trying though
I am in the US and could not imagine Amiga without DiskSpare. 1.96MB on an Amiga high density disk
@@saganandroid4175 You had/have a High Density Amiga floppy? Nice...
@@RobSmithDev - There was a similar floppy disk method on the C64 achieving incredible read speeds. Write was still slow but the read was 10x or more faster with some gap tricks. I think it was called Express or Jet Load.
Most of the reasons for not putting more on the disks were due to reliability issues. The Disk drives,heads and physical media all added up to issues if you tried to store too much onto it. 720kb (for PC) was a safe standard for everything.
Interesting stuff indeed, I typically formatted disks on the ST at 820K (82 tracks 10 sectors) as I found 11 sectors to not be 100% reliable a lot of the time.
These tricks remind me of a pair of programs for the PC, FDFORMAT and its TSR support program, FDREAD. They allowed you to do some tricks such as reducing the number of root directory entries to a single sector (which, perhaps surprisingly, was compatible without having to use FDREAD) and adding sectors to each track and adding 2 extra tracks (82 tracks instead of 80). Using such tricks, a 1.44MB HD floppy disk could store something like 1.76MB (I'm not sure of the last digit). But if you wanted to store a single file which was just a little too large for a floppy disk, reducing the number of root directory entries was a useful trick which meant that the disk was still usable in any MSDOS machine without needing a support program.
ב''ה, if you're interested in this, OS/2 XDF is a hazy memory and a source of significant headaches, but IBM was trying to squeeze room out when Warp (3.0) still came on floppies as well.
FAT12 and FAT16 Boot Records have an field that specifies the number of (8.3) root directory entries. The value in this field will determine the root directory size. The "normal" number of root directory entries is 512. Since each entry occupies 32 bytes the "normal" root directory will occupy 16384 bytes or 32 sectors. Dropping the number of root directory entries to 16 will give you 31 more sectors for data without confusing DOS.
@@josephkanowitz6875 PC DOS 7 was also distributed on floppies using the XDF format. The XDF TSR allowed DOS to use a floppy with this format. The XDFCOPY utility is included for duplicating XDF formatted floppies.
@@oledave2540 That's exactly what I found in my investigations. If you change the boot record to say that there are only enough root directory entries for a single sector, then the root directory will only occupy that single sector, leaving the rest available to be used as storage. It was just right if you only needed a tiny bit more space and you were storing only a few files, using the root directory only.
I think this is the first time I see this YT channel, and I'm positively surprised with accuracy of ST's tidbits. Been playing around with floppies back in the day (ST 3.5/5.25/SD/DD/HD, synchro express, 800's 1050/551, etc.), and watching this was a nice flashback.
….you’ll like the next one too, but that won’t be out for a week or so
Oh there were so many ways to format floppy disks! :-) Not just what personal and home computers did but also other hardware that used them. Early PC disk maintenance programs could do things like interleave the sectors which often gave a significant speed boost. And then there were formats with varying sector sizes. I believe the Ensoniq Mirage did this, giving the sampler just a little bit more savable storage.
I remember, it was pretty common in 90's to format HD disks with 20 sectors per track and 82 tracks, obtaining even 1.6MB capacity. And it was completly not a big deal to format a DD disk to 10 sectors per track (800KB). I'm talking about PCs.
Amazing the flexibility of the way floppies can be addressed (and how flexible the hardware is to allow this).
The Amiga floppy interface was flexible because it was quite dumb and simple - the Paula disk logic was basically a shift register and FIFO buffer sitting between the floppy drive data lines and the DMA engine. The status and control signals were connected to I/O pins on the CIA chips, relegating all the drive control tasks to software.
Even the MFM decoding and encoding was done by the software (some loaders used the blitter for this).
(Yes, there were a few extra features I didn't get into, such as wordsync)
Really interesting video and will be interesting to see this in DiskFlashback
Regarding labels, yes I remember that - my basic theory, a previously re-used "recycled" disk was likely cheaper than a brand new disk, and at a certain point towards the end of software being supplied on floppy disk likely a massive collection of surplus/spare double density disks previously duplicated and labelled for predominantly PC software ended up being returned, and possibly because PCs moved quickly towards high density disks a certain amount ended up being repurposed as Amiga magazine coverdisks. P.S. disk re-use also happened with PC format coverdisks too.
Interesting - thanks for sharing!
Very interesting and informative video Rob
Thank you
Learned a lot on this Rob, thanks 👍
Great video again Rob, amazing info of the humble floppy disk!
wow! interesting disk optimisation. Not just users but curious hackers. That's the spirit!
That brings back memories! I remember using that file system as a means of backing up my hard disk. The backup program also compressed the data, so attempting to use as few floppies as I could get away with!
Awesome
Really interesting. I had loads of AUI disks and never ran into any issues with those disks.
I have a few of these disks in my archive stash, now I need to go get them and take a look.
Disc duplicators would always use new discs because they were more reliable, however sometimes they didn't. What would happen is that there were shortages that sometimes occurred. It's not a shortage in that floppies became scarce on the shelves, but in bulk purchases. When duplicators bought discs they bought by the thousands at an extremely low price. When they couldn't buy at that low price they went to disc reclaimers who were supposed to clean the labels and blank the discs (at one place I knew of they would literally hose off the discs with just tap water then scrape off the labels and then run big magnets over them and lastly hang them up with a fan (those were the super cheap discs! no returns). But sometime when deadlines were crazy shortcuts were taken and you get a huge box of all different discs with whatever was on them "good luck"
Wow I never realised it got so crazy! - thanks for sharing, very interesting!
Nice one! Tracks and sectors constantly remind me of XCopy 2d grid (8 rows by 10 columns + unused 9th row that can only have 2 columns - guess that'd be some extra for the DiskSpare?), or "formatting cyl 0 of 79" formatting disks in AmigaDos.
Lol at the "that's what FFS stands for, not what you're thinking!" 😆
Sounds like some of the tricks Apple did on the classic macs. (the outer tracks had more sectors) And the Microsoft "distribution" format pushing the DOS/Windows install discs to 1.68MB. (written track-at-a-time with no sector gap)
Reminds me of the various “super floppy” formats, like floptical and ls-120.
Ahhhh memories… I us to use 83 tracks and 11 sectors on my ST.
I loved DiskSpare! Got 1.96MB per disk with my high density floppy drive.
BTW the 837K for OFS was, the actual usable storage space VS the 720K "PC" disk which was the theoretical max including the filesystem overhead. Really, the PC had far less than 720K actually usable space. I seem to recall the FFS came out prior to KICKSTART 2.O.
Yes, but FFS prior to OS2.0 was only for Harddisk
Actually, Atari ST formatted disks could be read on DOS-PCs directly, if these were formatted either with TOS 1.04 upwards, or a 3rd party formatter like Hyperformat. Only TOS 1.0 and 1.02’s formatting routines had a bug that prevented DOS recognizing the disks from the ST. As you mentioned, the other way round (PC->ST) was never an issue.
The 1st program on the ST to go beyond 880KB was Hyperformat from Claus Brod and Anton Stepper.
TIL that the Amiga went far beyond 900KB! Its "full track" tricks can’t be done on the ST, as this one uses a "classic" floppy controller WD1772 that works per sector.
How Floppy disks actually work always makes my head spin. The multiformat disks always seem like magic to me. A disk that can be read on the Amiga, Atari ST and DOS!
……that’s the next video, but you’ll have to wait for it :)
@@RobSmithDev I have a bunch of them that came with an Atari ST I picked up in a charity shop over twenty years ago. The floppy drive had been replaced and was upside down if I remember rightly. I only booted it up a couple of times because upside down disc drive was a bit unreliable and it's sat in a cupboard since then. I've ripped the discs as I was curious to have a tinker but the flux images have also just sat barely looked at.
I think thankfully they’ve all been captured and saved down for preservation which is great
Cool stuff Rob. I had not heard of that format as, being from Canada, I had subscriptions to AmigaWorld and Amazing Computing, and the only UK magazine I regularly bought was Amiga Format. I do recall AUI but for some reason it just didn't appeal to me.
I recently built a DrawBridge using a spare Arduino and have been having fun with that. Thanks for all the cool stuff you are doing with these great old machines. Any chance you will be attending this year's World of Commodore show in Toronto? 😄
Glad you’re enjoying drawbridge! It’s very unlikely I’d be able to attend d the WoC show but thanks for asking
Some Amiga magazines published an occasional dual format disk that mixed in ST formatted tracks in areas that weren't strictly required by the Amiga OFS.
Also, FFS was available for hard drives, but I'm not sure if it did similar low level trickery as with floppies. I remember it being perceivably faster with caveats - pre-2.0 Kickstart ROMs could not boot FFS partitions although these could be mounted after booting off of an OFS partition, and, there were people who backronymized FFS for what you actually WOULD think because they had their FFS partitions get repeatedly corrupted.
I remember there was some software for the PC that could also, with some disk controllers at least, write a "huge" extra amount of data on DD and HD disks... also I managed to buy some cheap disks of questionable quality that were not very good at the standard HD format, but when I configured a standard 3,5'' HD drive as a 1,2MB 5,12'' drive in the setup as my B drive, it would happily use that (almost) 1,2MB per disk without issues, while in 1,44MB format those same disks would have so many bad sectors that the usable space went way below 1MB. It is possible that these were actual old DD rusts packed in HD shells and wished Bon Voyage. This seemingly goes to show that the disk rusts had a rather sharp limit of frequency they could reliably record, and lowering the recording frequency only by approx. 17% made them work way better.
I’ve got a video coming up on the dual format disks - they’re interesting in their own way. Not all hard drives allowed you to change anything to do with sectors - some were ‘hard sectored’ and those were the ones that if you low level formatted them couldn’t be used again.
It doesn’t surprise me that some (later) pc controllers had more control over the disk
I remember having a few coverdisks on old reused disks.
This reminds me that I remember xcopy by default didn't copy past 79. I sometimes wondered if games that didn't work after a copy was because I never added those extra sectors.
xcopy didn't actually have anything to do with it. You could load the dos floppy.sys driver and give it the right arguments to access a floppy with different geometry, but most people didn't, and so floppy access was left up to the PC BIOS ( int 13h ), which normally had a small menu that let you tell it that you either had a 720k or 1.44 MB 3.5" floppy, or a 5.25" floppy . If you told it you had a 1.44 MB 3.5" floppy, it assumed 18 sectors per track and 80 tracks.
@@phillipsusi1791 He means the Amiga software named X-Copy... a different animal. This was a track-to-track disk copy program that had some extra tricks up its sleeve as well, namely copying disks with non-native encoding. It could at least theoretically duplicate any disk that didn't exceed 82 tracks or didn't require using a higher frequency to record a track than what was used for the 11 sectors.
I remember attending one of the early Assembly parties, I had my trusty old Amiga there... ended up discussing the different disk shenanigans with a PC user, and showed them that not only I can duplicate the DD disk we were given to store our votes, but I could mount the disk for file access, and even run some of the simpler PC programs in the PC emulator.
@@jussikuusela7345 Ahh, I remember playing games on Amigas in an Amiga store next to the landrymat where my mom worked after school, the the kids of the people who ran the Amiga store. DOS also had an xcopy command that was just a better file copy command, so I thought that is what was being talked about. I'm not familiar with the amiga one. It sounds like you are talking about something more like the unix dd utility that just read and wrote each sector on the disk without regard for the filesystem.
With Atari st the max was with most of dd drives was 83 tracks and 11 sectors, 913 kb / 934 912 bytes formatted so that the formatted disk was accessible without any extra utilities.
I discovered Diskpare on an Aminet CD that i purchased in the 90s. I used it on my A1200 it was brilliant being able to store all my music modules and instruments disks. I think i did and test with 10 of my most used disks and managed to cut the 10 down to 7 disks. Shame it couldn't be used to increase the size of my 60Mb hdd inside the A1200.
I suspect the 60MB probably had "hard" fixed sectors, so more couldn't be added, but still, would have been cool
Slight variance in speed would only be a problem if writing to the floppy, it would overrun and corrupt the first sector. I suspect most cover disks didn't write to the original media. ST allows whole track read or write but the problem with track write is that some values are reserved as commands to create gaps etc so is less versatile than the Amiga there.
Meanwhile: *me looking at the 1.78 MB floppy disk library in my Cardboard Box Of Old Stuff*
i remember having a HD floppy (1.7mb?) on my A1200 tower. i think it was just a slowed down DD, but i might be wrong. It would be good to get a similar deep dive into that. I think A4000 had a HD floppy? good vids for us fellow nerds
Yeah the HD drives just span the disk at half the speed so could fit twice as much, there’s not really that much more to it other than some signalling that went on to tell the Amiga it’s an HD disk.
This brings back memories of my KCS Dual HD Drive.
Peeling back an early ST/Amiga Format coverdusk revealed the retail version of Oids
I have a (now broken) Amiga copy of Utopia where the disks were old copies of an Atari game Federation of Free Trade, printed directly on the disk, but the Utopia label was just stuck on top of it. I think when they needed some stock of one game, they'd just take whatever disks they had from unsold stock and just write on top of them.
Ahh, Utopia. Such a great game.
I bet your next video will be announcing your major breakthrough getting a standard Amiga floppy disk to store a megabyte
Well I did manage it…. But the Amiga wouldn’t read it
@@RobSmithDev due to hardware or file system limitations?
not sure tbh I think the software may have been ok but I think I may have pushed it beyond some thresholds
@@RobSmithDev and wasn’t just a bad disk?
@@sacredbanana no, read fine from my PC. I pushed the ‘long track’ thing a bit far I think.
Do you know how MacroSystem did this on the DraCo with their DraCo format floppies? They stored around 900kb on a floppy, twice that for HD floppies. DraCo can read/write regular Amiga formats as well. And has Amiga DOS drivers so your Amiga can read DraCo formatted floppies.
Cool, makes sense
Great video 👍👍
The Acorn ADFS type F format allowed 1.6Mb on a standard floppy.
I’ve yet to look into Acorn disks. On my list for sure
One thing that's worth considering is that I used extended formats to squeeze almost 1MB out of my disks on the Atari ST. However, 30 years on those disks are completely unreadable, I imagine it was a combination of imperfect storing conditions, cheap media (poor student) and pushing the media past its specifications. I was a sad man when I lost all my code from those years. I really should have copied the data to a hard disk or something when I first started getting into PCs
Storage of disks in a dry environment was important. I have loads of disks from that time period that work perfectly but I was just lucky. Sadly though like you, I have a few that are beyond their life
wow and peace be upon you sir from me
I still have my 1.76.MB Drive on my A500+ which can be format to nearly 2.MB.
In have 3 external floppy drives in total which were put to good use on games that were on many floppies.
very interesting! talking about atari st and amiga disk formats, i had a flashback... and now a request: could you also make an explainer about the "argonaut dual loading system" used with the starglider 2 game?
Not that one specifically but I will be covering the dual format Amiga/st disks
@@RobSmithDev Rob Northen type?
I always used 1.7M HD Discs back in the days on my PC formatted with VGACOPY. If I remember right it goes up to track 82, but I think sectors didn't change or I can't remember.
I had quite a few with labels underneath but I don't think they were second hand. I can only imagine towards the end they were using whatever disks they could find at the cheapest price and that must have included (unused) discs that had prior software on them.
Ah yes that does make a lot of sense.
I always thought it was the indexing, like the TOC used on CD-ROM's, MS-DOS used error correction as well, and I assumed the Amiga didn't bother.
software publishers would send the unsold software to get recycled.. they would magnetically erase the disks and bulk pack them for software distribution publications like the aol mailer and magazines.
Makes sense, and explains a lot - especially the many AOL disks
I wonder how much they could have packed if they started using variable drives like the commodore floppy drive used to. EG there were four zones from the inside track to the outside tracks. If I remember correctly they varied the bitrate. That's why they can put more sectors on per track as they went to the outer tracks.
The reason was fairly simple there was more track length on the outer tracks versus the inner. So it wouldn't overwhelm the the media's ability to distinguish between the bits on the track
I suspect the extra complexity involved is why they didn’t - and would have needed a specially made drive I guess. A bit like the earlier Apple drives. But yes then much more data.
The limit was never really the physical medium. It was the ability of the electronics to operate at higher bit rates, which they would have to do in order to do that.
Great video as always Rob, Never heard of diskspare before today. that would have been super helpful back in the day too! Great to hear flashback is getting an update. Wondering if there's any plans / way to add apple support to it? I've been using my drawbridge floppy for all sorts lately but apple disks caught me out lately.
Depends with Apple, from what I understand there’s two different formats - but that’s as far as I’ve looked so far
On PC under DOS ther Was VGA-Copy that could do more and IBM's OS/2 by default (in 3.0) came with XDF making a 3.5" 1.44 carry 1680 kiB
All but the first 2 or 3 floppy disks that Windows NT 3.50 came on also used that 1680 KB format. I started using Linux around that time and managed to get 1920 KB on a floppy using a mixed sector size format.
DiskSpare got 1.968MB per Amiga HD diskette. PFS allowed even more IIRC.
3.5" DSDD disks were advertised as 1MB unformatted and DSHD, 2MB. The actual size was obviously determined by the various platforms and filesystems as per Rob's coverage here. Question Rob, how did you produce the graphical representation of what the disk surface looked like?
Huh? DSDD 3.5" disks were advertised as 1.44 MB, because they held 18 sectors per track and 80 tracks per side, for 1440KB. Then they came out with those high density drives at 2.88 MB but floppies became obsolete before I ever got one of those.
There’s a program called HxD floppy emulator that will do this from disk images. I changed the colour scheme to suite me. It’s a handy tool for checking backups etc are ok
@@phillipsusi1791 Unformatted VS formatted. Formatting uses some of the theoretical space for sector indexing etc. You could write a proprietary code to store as much data on a disk as the controller, drive mechanism precision, and disk rust quality allow, but that would at worst be very touch and go with any other drive and controller than the combination you wrote it for. Instead the standard PC formatting uses a recording frequency that is in a fairly well proven range, and inserts indexing data and padding that are not seen as user data... Amiga uses a slightly higher frequency and arranges that padding and indexing in a different way, allowing approximately 22% more storage on the same rust, actually getting fairly close to the theoretical 1 or 2 MB unformatted specification.
@@jussikuusela7345 You can't really talk about the capacity of an unformatted disk, therefore, all of the capacities I have been speaking of are for formatted disks. The standard PC format used 18 512 byte sectors per track, times 80 tracks, times 2 sides, to store 1440 KiB. There was a Linux tool called superformat that could instead format the disk to use, I think it was only two sectors per track, one that was 16 KiB and one that was 8 KiB to store a total of 1920 KiB, by reducing the overhead of the sector headers. You could not control the raw bit rate or rotation rate of the drive, all you could do was change the sector size and try to find a combination that the drive could manage to write to the track before the first bit came back around again. I feel like you may be confusing the two different kinds of formatting. People used to speak of a "formatted" disk as one that you ran the DOS format command on, which would write a FAT12 filesystem to the disk. The filesystem of course, has some of its own overhead to keep track of what clusters belong to what file, and store the names of the files, but that is very different from the low level format, which laid out what sectors existed in what position on the disk.
@@phillipsusi1791 Actually, 1440KB was HD and 720KB was DD.
Fun fact - Double Density disks were used with MFM encoding, which could encode twice the number of bits compared to the earlier FM. Because the MFM scheme always had at least one 0 between two 1 bits, you could double the number of bit cells in a track while maintaining the same flux reversal density - essentially squeezing an extra bit cell between two flux reversals.
The AMIGA could also write and read 720k DOS disks with FAT12.
Yes it could, and several other formats
So it is kind of like Shingled magnetic recording (SMR) in some hard drives. Can you try this trick on 1.44 HD and wishful thinking 2.88 ED Disks. Only wish that 2.88MB disk became popular in the day.
Awesome never knew this. Traditional standard HDD floppies can only be seen with KS 2.04 and WB 2.10 or higher 1.76MB FFS or 1.67MB OFS.
:) unlike a lot of people my entry to the Amiga was the A500+ so I started with Ks2.04, DriveID - how the Os discoverers what type of disk is inserted is interesting though
@@RobSmithDev A500+512 Expansion back in 1988 then the good old A2000. Mind just boggles how it knows. And having just bought a modded PC drive to read HDDs just shows how much wasted potential there was.
@@RobSmithDev 2.04 can see OFS 1.67 HDDs however i found theres no FFS option unless you use WB2.1 Thanks for the like.
Nice video
I suspect if PCs was just as reliant on floppies as the Amigas, they would properly have done this too.
I don't exactly remember if it was PFS or SFS or what other name but I'm pretty sure I've been using some filesystem that let me write over 1MB on one DD disk. I think it was actually a question of settings in the filesystem settings file where you can set the block size or something like that.
Yes changing the block size would help - but this is close to the physical limits of the disk. I doubt it was PFS or SFS as they were mainly used on hard drives but I know there was another one and I don’t remember its name
@@RobSmithDev There was AFS (AmiFileSafe) which i recall getting from a cu amiga coverdisk. it later became PFS I believe or it was the floppy part of it.
Thanks for reminding us of AFS and PFS. Yes as l recall they did work on floppy drive. Atomic Commit included. I seem to recall PFS allowed even longer filenames.
The drive speed wasn't critical, there's a phase locked loop to cater for different speeds. So long the speed was mostly constant. Ie a clicky floppy disk slows down rotation for and instant. Still in many cases the disk could still be read if the controller can adapt quickly enough.
If drive controllers could vary the flux transition lengths more could be stored on disk until you hit the magneting density limit. Higher frequency pulses loose their signal strength quicker. Varying pulse length per track would've been possible though.
Same with what they did on the LS240 using standard floppies, because the more precise (but lot more expensive...) drive could simply "pack more". That is, assuming your magnetic substrate wasn't total dos**t like it was the case for "no name brands" of the day...
This is true a, but machines like the Amiga couldn’t - they had a fixed clock for writing so couldn’t ‘cheat’ like that. The drive speed is Important, sure for reading there’s the PLL, but writing, well it literally can affect how much space there is
I had a program on the PC that formatted a disk to 1.9MB instead of 1.44MB. No idea anymore what it was called, probably came from a shareware CD. Or a magazine.
I think the later hardware could do this but not the original
Not sure if you covered it already but what is your background with all this? Were you a copy protector dev back in the day?
No I wasn’t. I made Drawbridge and the Floppy Bridge plugin for WinUAE as well as DiskFlashback so I’ve had to understand a lot about low level flux stuff to make all that work.back in the day I only ventured as far as Amos
@@RobSmithDev well your videos are absolutely amazing and a treat to watch! And I never even had an Amiga back in the day (386sx-25 home PC user). Keep up the fantastic work bud and have a great week!
@@UXXV thank you 😃
i wonder why they didn't go to 1024bytes sectors, as it was common on PCs. or even different sector sizes per track. so you could minimize the total number of gaps per track.
Huh? Standard PC disks used 512 byte sectors too.
@@phillipsusi1791 Standard, but this video is about "super density formats". 828kB on 2DS floppies was a widly used format on PCs. but this was not the limit, when making disks for drives with better tolerances.
Thing is, the file systems typically can’t store more than 1 file per sector so the larger the sector size the less number of files you can fit - so it’s a little bit of a trade off
My AUI disk 87 (Aug 96) also had its label stuck on another label: PTR Program/Graphics 1 from WordPerfect 1989.
Crazy!!!
Wait till someone finds the hole punch, easy space increase. Haha ;)
….it is, if you happen to have a high density drive which most Amiga users didn’t. And the hole punch trick had mixed results I think
I was a fond user of DS till i found an other Filessystem wich name i dont remember anymore ... I was able ot fit over 1.0xx KB on a Standart DD Disk... Sadly its been way to long to remember. While i always formated the DiskSpare Devices with DS0 the other one was maybe called FS0 ? gosh its been a while.. but blew my mind!
Aha! I wasn't imagining it! I've been trying to remember the name of that one too. As far as I recall, it could squeeze about 1.2Mb on a DD floppy. The size sticks in my mind because I remember thinking how ridiculously close it was to the capacity of a high density PC disk. It wasn't as robust as DiskSpare, though. Despite its trickery, that was rock-solid.
[EDIT: I think I've found it. I'll post a new comment.]
@@duncansnowden6857 i dont see your comment, whats the name ?
@@VividNation Strange. I can't see it now myself. I definitely posted one.
Anyway, I realised that I'm still using my old disk image from back in the day with UAE, so I had a look around it. There's an FS0 DOSDriver, and a “floppy.device” in DEVS. I'm sure that's it. I *think* it was called Floppy Filesystem.
@@duncansnowden6857 Got it!! Its on the Aminet and called Floppy43.lha and can pack a whooping 1148KB on a DD Disk!
I never had any problems with DiskSpare.
There was another one that could fit even more data on the disk. 1.1 mb rings a bell, but I can't remember what it was called.
Yes I recall there was another but I don’t remember what it was called either
IIRC - If we wanted to get that mythical 1.1 Mb capacity on a DSDD floppy disk we would use
xfloppy.device
IIRC - If we wanted to get that mythical 1.1 Mb capacity on a DSDD floppy disk we would use
xfloppy.device
AFS or PFS?
Oh I use to buy boxes of disks from a company calling themselves 'Chickenshit Software' and pretty much all their disks were recycled old versions of PC software, thier labels were so sticky it was near impossible to get them off but a hot water bottle would soften the glue enough to let you carefully peel it to reveal the original contents, if it was interesting then you could usually 'unformat' the disk.
Did you find any interesting software once ‘unformatted’ ?
Wasn't there also a trick where you altered the disk read process. I think shadow of the beast used this to cram onto disk far more data than was normally possible
It was probably using long tracks if it needed to store extra data. Has to be written using an external device as the Amiga can’t write them, but can read them.
Have you tried sticking one of your custom floppies into a stock Acorn Archimedes, running RISC OS 3.1 (1990), or later, as notionally capable of reading, in addition to Acorns own 100 / 200 / 400 / 640 / 800 / 1600 KB DFS / ADFS floppy formats (SS SD, DS SD, DS DD, DS DD, DS HD), assorted Atari ST, and IBM PC FAT floppies. Not sure about the Watford Electronics and Solidisk disk formats, that those companies sold ROMs advertising more space per disk than Acorn, for the BBC micro.
You also missed the Mitsumi QuickDisk system, that used a spiral track, and appeared on the MSX, Roland synthesisers, ...
Hehe I didn’t ‘miss’ any other formats because the video wasn’t about that. It makes sense though that the Archmides could do a better job, it was a later system so was probably designed more flexible/do it in software rather than hardware
The Amiga 4000 supported HD disks, formatted in its own and FAT formats. While the QuickDisk systems, sold for some MSX, Nintendo, Roland, Spectrum, ... didn't use sectors, just end of file markers.
Also possible on PC with 2M, even pushing as far as 1066
Some of the later floppy controllers could but the original ones couldn’t
Wrong, the original ones could, I used it in an XT exact-clone. Also 2M would replace the BIOS allowing to use 3.5 drives in old computers (HD ones required replacing the controller, DD ones didnt).
They had two formats, 2M changed the number of bytes per sector (but same for the whole track) and the number of sectors per track. While 2MGUI also used different sector sizes in the same track.
Kryoflux was unable to read 2MGUI of any kind a few years ago 😂.
Thing is the Amiga could do this trick even easier as they could use any encoding (2M was limited by the 765 derivates), as was done to read Apple’s GCR, so I always supposed someone did that, playing with Paula?
fascinating. I guess, there is no way to slow down the disk during reading and writing in the outer sectors. otherwise, you could squeeze 1,5mb on such a disk.
Unfortunately not. I think the added complexity of controlling the drive speed is why this isn’t a thing on these drives.
"The average Amiga user only had a floppy..." As an ST owner, I agree. 🤭
Now now, let’s not start a platform war lol
@@RobSmithDevPlatform wars are childish and pointless which makes them a stupid thing to engage in. I never understood them even back in the day - it was so obvious the Amiga was & still is the vastly superior platform you'd have to be literally blind to not be able to see that.
As an Amiga owner back in the day, I had a big hard one. Big being 20Mb .... it's not the size, it's what you do with it that counts.
interesting video but very annoying that you don't have subtitles. the auto subs are pretty good. why deactivate them?
I haven’t deactivated them. Proper subtitles are only there if I spend *ages* adding them - it’s a manual process
@@RobSmithDev youtube provides automatic captioning and this works quite good since years. sure, they are not flawless, but much better than nothing. that's automatically active usually. so you turned it off apparently.
I haven’t - they just may not have auto generated them yet - and I’ve just tested and they’re working for me
@@RobSmithDev nice, now they are available here too! ty!
the Floppy i know had 1,44MB (1,38MB with a filesystem)
Sounds like PC FAT12 to me
If you want a good understanding of some more formats (why the apple ][ only had 144kb a disk for example on the 5.25in disks) then there's some nice manuals from the copy protection programs out there. I had book of 3 or 4 manuals together at one point. I think it was locksmith, Nibbles away and another manual. Really informative about disk formatting and concepts like track arching and so on.
2M on the IBM PC is one of the best resources for high density floppies on that system. I think 2m source code exists out there somewhere?. Teledisk/Anadisk are also fantastic low level formatting/copying programs for the IBM PC and you can learn a lot about formatting etc. You can make stupid high density disks on ibm like 20mb but if you move/tap or breath on the disk it just breaks. It's possible to "store" data on it but it's highly unreliable.
Amazing videos as usual
I recall a utility I had for PC that would format a floppy to more than 720k and it was usable in dos. Some of my disks are formatted with it and I can’t read them in windows 😂 (or they might just be bad 🤣)
If they didn't use the standard format, you had to load a driver to access them in DOS. Windows is going to be expecting the standard format, so if it isn't that, it can't read it. The Linux floppy driver had a bunch of different /dev/fdXXXXX devices for non standard formats and if you used the right one that corresponded to the format of the disk, you could access it.
ב''ה, Y'know, buying Hertzfeld a copy of "On the Edge" could not have gone more poorly
?
DD disks were 1.44Mb... Or am I losing my minnd??
The Amiga and PC's used the following capacities for their standard disks =
Amiga capacities =
DD = 880 Kb
HD = 1.7 Mb
PC =
DD = 720 Kb
HD = 1.44 Mb
Naw, 1.44MB disks are HD disks...
Yes you’re losing your mind 😂 that’s the capacity of a PC High Density disk. The Amiga could fit 1.76MB on those and if you used DiskSpare you could get upto 1.9MB! - but not many people were lucky enough to have a high density drive on the Amiga
@@RobSmithDev Was never an Amiga guy.. I was... an Atari guy.... ;)
@@RobSmithDevI had one of the dell external floppy drives that were sold with an Amiga cable. I'm not sure how many of them were sold, I think it was just a batch of drives that someone found in a warehouse. At the time they came out, there was no reason why you would need a half speed floppy drive on a pc.
What was I thinking
Huh? wasn't 720k single density? Double density was 1.44 MB. I remember using superformat in my early Linux days to cram 1920 KB on those by using mixed sector sizes. Microsoft did something similar to fit more data onto the ~40 floppy disks or so that Windows NT 3.50 came on. The first 2-3 disks had the standard 1.44 MB format so they could load the drivers to access the extra capacity on the rest. You could get extra capacity on floppies in DOS by loading the floppy.sys driver with the right arguments too. And I also did format some disks with 82 tracks. I sometimes had trouble reading them back through on computers other than the one that formatted the disk. When I was in college, an open source Windows NT clone called ReactOS came out and I contributed to that for a while. Including writing the floppy disk driver. I was very confused as to why the driver worked fine in the bochs PC emulator, but not on real hardware. It turned out that while the floppy controller specifications said there was a command to probe the geometry of the drive, no actual hardware ever actually implemented it, which is why PC bios always had a screen where you had to TELL it the type of drive you had connected, and both the Windows and Linux drivers just used the geometry the bios said to rather than try to probe it.
1.44MB is high density. Single density is 360KB.
@@MurrayDagostinoAnd extended density was 2.88 MB (actually 2880K) but was never widely adopted
@@MurrayDagostino Wait, so there were FOUR generations of 3.5" floppies? I only remember three: 720k, 1.44M and 2.88M if you even count that last one. Before that I remember 1.2MB and 600k 5.25" drives. I only ever remember PC BIOS having the choices between 720k and 1.44M for 3.5" drives and 600k/1.2MB for 5.25".
@@phillipsusi1791 There was 360KB 5.25" floppies as well and even 180KB on the Commodore 64.
@@MurrayDagostino Oh wow, the C64 ones only held 180K? Man... load somethingorother,8,1.... play game!
So that is how DiskSpare worked: I AM DISAPPOINT! I thought it was a whole lot cleverer than that, using alternative MFM encodings. If you have stared at MFM bitstreams then you have seen that there are legitimate bit combinations that will never be generated by the standard encoding method. To try to use that you would have to build a bitstream much like arithmetic encoding where you can never know what the data represents before you have decoded everything coming before it. The possible size savings seem non-deterministic and depends on your data - you might want to try strategies to massage it to get a more favourable position.
I guess there’s two reasons why this isn’t done. The first is it would make the encoding and decoding far too complicated for the electronics of the time - or at least, too expensive. The other is if you were using a standard floppy disk drive then you have to be careful with the minimum and maximum time between flux transitions. I’ve explained how at a low level this works in a much earlier video. Plus those ‘not normally encoded sequences’ are useful to trigger things (eg sector start sync words)
@@RobSmithDev I am talking about 100% in-spec MFM standard, but it needs to be software en/de-coded (well, nothing says you can't make hw for it, but on the Amiga you only have the raw data anyway). There is a long thread on EAB where we discussed it.
Is 2024 now not 1990.
And there’s lots still to learn
Floppy discs were recycled.
*sigh* ffs....
Lol you sound like a chip munk 😀
……no, that was this video:
ruclips.net/video/UBEo4ezaw5c/видео.html
@@RobSmithDev haha 😂 OK that explains it. But why do you use that thing on your voice all the time?
try a ls240, 240mb floppy
Ha yes, but that requires a specially made drive LS drive!
@@RobSmithDev no it doesn't. I can send you mine. i used it to recover data and used it to run an entire tinyxp off it.
@@werehyenataurthanks for the offer :)
You wave your hands around WAY too much. Couldn't watch the video for any more than a few seconds, sadly. Sure it would have been interesting too.
Never mind, it’s called being expressive