Debugging the 1959 IBM 729 Vacuum Column Tape Drive at the Computer History Museum
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- Опубликовано: 3 июл 2024
- Our magnificent IBM 729 7-track magnetic tape drive is giving us read and write errors. We attempt another heroic repair. Which is a great excuse to take a close look at its amazing innards. Looks like nothing in the video, but just putting the 3 brush blocks back was a 3 hour operation with mostly 6 hands at a time inside the drives - including mine, which is why there is no video documenting it. Hence the clapping at the end, we were quite relieved we did put it back together correctly!
Tape capacity is around 20 MB at the highest (800 cpi) density setting. Actually quite respectable if you compare it to this machine's main memory (16KB).
Credits:
Special thanks to Samtec for fabricating and donating the IBM-spec special wire. Extra special thanks to Shashi Chuganey for spooling the wire from scratch at our Oregon facility, and to Raymond Lee for silver epoxying them in our clean room facility in California. Also thanks to CHM docent team member Dave Bennett for finding a commercial source of replica brushes. So I didn't have to do the 92 production ones after the first 8 hero prototypes...
Many more people were involved in getting these tapes operational, but limiting ourselves to the ones that appear in this video:
Ignacio Menendez
Glenn Lea
Carl Claunch
Stan Paddock
Related Links:
Official video of our IBM 1401: • 1401: The Dawn of a Ne...
Period video introducing the IBM 1401: • IBM 1401 French Presen...
Robert Garner's blog article about the restoration: www.computerhistory.org/atchm/...
The restoration team's hardcore technical website: ibm-1401.info/#WhatIs
Our sponsor for PCBs: www.pcbway.com
Support the team on Patreon: / curiousmarc
Merch on Teespring: teespring.com/stores/curiousm...
Learn more on companion site: www.curiousmarc.com
Contact info: ruclips.net/user/curiousmarca... 
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When I was a boy in the '80s I used to think that every time an old movie or TV program showed a mainframe's tape unit, their prop department had gotten it wrong. I was used to playing around with my father's old Akai reel-to-reel tape recorder, and my grandfather's Wollensak -- the reels both turn in the same direction and at the same time. It wasn't until many years later that I was able to research IBM's vacuum-column technology and appreciate how innovative and impressive their tape units were and still are.
Same here!! Thought I'd try to find out what was happening :)
We had some old mini-computers that used 9-track reel-to-reel tapes like these (but not exactly, ours were made by Pertec). When we had some 'suits' scheduled for a tour, we were told to 'Make it look like the computer is doing something'. So we would queue up an old tape-to-tape sort program (even though we normally did large data sorts directly to the disk drive).
So when the 'suits' came in, they got to see the reel-to-reel tapes jerking back and forth, just like old movies and they were duly impressed. lol
@@mikefochtman7164 At my company we ran diagnostics to make them look busy for a TV crew. 🙂
It's rather beautiful to watch that tape machine work. The action of the reels is rather soothing and hypnotic.
I'd have it over a lava-lamp any day.
It was more than Hypnotic. I worked for Honeywell in the sixties and one customer Unbrako in Coventry England had eight tape drives. I used to run systems check which operated EVERYTHING. When these monoliths ran, writing, reading, fast forward and fast back, it was like an orchestra playing. The low growl when reading back and the high pitch on the rewind. I wish that i could have recorded it. Music to my ears.
You think of the detectives waiting for the investigator researchers to get a computation result. The tapes are spinning and the film noir detective is waiting and pondering what the results could be alas an op code is invalid.
You're the only one to make a video showing the inside of these! Thanks for the interesting video, I've wondered how those worked
LeiserGeist Bobby
*That boy ain't right.*
I would never had guessed the existence of that vacuum tape buffer system. It's like a mechanical cache, genius.
Blue screen "Read/write error sector 00001011"
IT technician starts the lathe.
Awesome video!
Locutus of Borg encountered a write error at sector 001
Maybe because all the Borg were sleeping.
Benoit De Brueker Naaah, oscilloscope!
Sector 11 in big-endian? Or sector 208 in little-endian?
We're talking about an IBM machine, that'd be a read/write CHECK ;)
Flew out to fix another brand VC tape drive once on a support call. Tape kept sticking / snapping in the columns. I finally found some kind of sticky goo in the back corners of the columns. I asked the customer what they were using to clean them... It was wintergreen rubbing alcohol, which contains a plant oil/sap.. Cleaned them with pure alcohol, and it ran perfectly. Informed customer about proper cleaning chemicals..
Many years ago I refurbished an IBM 727 tape drive (predecessor to your 729). The 727 had vacuum tube logic (plus lots of relays), but the motor drive design was almost the same as your 729. The brushes were OK, but the powdered iron and graphite mixture inside the tape reel shaft clutches had rusted so the reel was trying (unsuccessfully) to turn both ways at once. Disassembly, cleaning, and reassembly of the clutches was a real chore! But I got it all working OK after troubleshooting a bunch of the vacuum tube logic - and learned a lot in the process.
Fabulous Video !!! I spent many hours inside the computer room of an IBM 360 and I was always amazed at the incredible speed and quickness of those tape drives, and the slack tape hanging down inside their vacuum chambers. When the IBM repairman came around, he was dressed in a suit and carried a suitcase full of the most beautiful exquisite tools. The type you might see in Switzerland. IBM made precision top world quality machinery, and the tools to maintain and repair IBM equipment were equally impressive.
Repairing mechanical equipment in a suit sounds like a challenge. I'm sure they had to get them dry-cleaned often too.
0:02 Notice the large panel flooring in this IBM 360 computer room. All the wiring and cooling for the machinery ran under the floor. The computer itself required this specially-built room, and computer rooms all looked quite similar in every company which owned an IBM computer. Beautiful space-age modern equipment. It still looks futuristic six decades later.
As an ex Magnetic Tape Drive Engineer working out of the UK - see this problem and how you resolved it brought back many sweet memories. Awesome work. I was smiling as much as you all were at the end. Bravo
The sound of that computer room brings back memories. They even have the raised floors ...love it.
Yep and you could keep your lunch cool down there. There were many occasions when I'd be working on cables, with my feet through the hole in the floor, getting very cold!!!
Well this neat, back in 1996 my electronics class disassembled a 1401 series computer, 720 tape drives and backup power system as a class project. At the end it all was sold as scrap metal
I did manage to keep one tape machine (I bought it for $50) and got it working, It's in my storage building now bubble wrapped up and tarped.. Along with a honeywell mainframe and hard drive rack.
I have a personal collection of vintage communications and computer hardware. I have one of the original World of Warcraft server blades also.
What's the spec of the WoW blade?
I'd buy the Tape drive & disk drives. But I already know your answer. lol was worth a try to get a bite
In my electronics class I dismantled a radar transmitter/receiver, complete with magnetron!
A little bit of electronics ? Geez, will you look at all those discrete components boards ! And 8 motors ! Wow ! What an incredible piece of engineering. No wonder it was so expensive back in the day. Fascinating piece of machinery. Thanks for this detailed inside view and explanations. Congrats to all of you on fixing it. This video made me subscribe.
What is the maximum digital data transfer speed of a tape unit like this ?
The maximum data transfer speed of this particular unit, a 729-II, is (6 bits per character) times (556 characters per inch) times (75 inches per second) = 250,000 bits per second. Other models of the same drive with a faster transport (112.5 inches per second) and higher density (800 characters per inch) could transfer up to 540,000 bits per second.
540,00 is only 67.5 Kilobytes per second or 0.067 Megabytes per second. Yes, it really was that slow.
Actually this hasn't really changed with modern tape drives like LTO; still a handfull of motors in those, just at a miniaturized scale.
@SteelRodent yes I know the struggle firsthand :-) I was referring to the original comment about the mechanical aspect and the number of motors.
@@simontay4851 same my internet connection...!
All that size, mechanical complexity, and electricity - and even an old junk 286 could outpace this machine with ease. It's astonishing how far technology has progressed in such a short period of time.
"even an old junk 286 could outpace this machine with ease" - actually no, these systems supported hundreds of terminals simultaneously. What they had that your 286 is lacking is THROUGHPUT
Every peripheral device in the system had an intelligent controller that was an entire computer in itself. I know because I was a mainframe computer operator in the 70s and 80s - you could not imagine a more fascinating job or place to work.
@@vap0rland I was a computer tech back in the 80s and worked in a data centre on several different systems.
@@James_Knott my favourite job of all times was computer room shift supervisor. I.B.M. really fumbled when they handed the industry to Microsoft on a silver platter.
It's amazing how much length they went through to run that tape at speed.
Watching the brushes being made was so oddly satisfying.
So iconic... I remember how computers were represented in any cartoon, until the 1980s: a cabinet with two reels 😊.
I love the mechanical solutions to electronic problems all through-out these older machines
Machines from when I was a young man. Good show on why those things were so expensive. Well done.
It's astounding to me the ability of the enginiers to design around the things they couldn't do in electronics.
Every part of this is a learning experience. I'd never even heard of silver epoxy. Now I'm left thinking of all the things that would have been the perfect tool for and I'd kludged. Well, if all you have is a hammer, everything looks like a nail.
OMG!!! my C: partition belt tensioner has broken
those connectors were epic
Tom P. They look like from the 1800s
Now _they_ are proper connectors! They will last forever.
The old bus and tag. I remember when we replaced those connectors with fiber. During the next big earthquake in California, the cables did not hold the disk drives in place anymore. They flew around the room as a result causing great damage. After that experience they had to retrofit special feet on the disk drives to keep them from flying around. Who woulda thunk that a fiber cable wouldn't secure those big drives to the floor anymore!!
We all need to stop & appreciate how these machines paved the way to the technology that we have today that we can wear on our wrists
What an amazing insight how these tapes actually work...
Worked on similar units to these as late as the 80's in the Air Force. They used them to load programs onto a CENPAC unit and run automated test stations for maintenance on F-111s.
Great video! I love 1401s, they were such a big improvement over the 402 accounting machine! Spent many happy hours programming these puppies. Almost wish I had one. :-)
One minor correction - disk drives existed at the same time as these tape drives. All the 1401 systems I used had multiple disk drives and no tape drives. Tape access was generally faster than disk access if you were doing a sequential update job, but a compile from a disk drive was a heck of a lot nicer than compiling from tape!
OK. I thought the 729 vacuum column tapes predated the RAMAC (first hard disk) by a bit. I'll double check. But yes, later on you could hook up a RAMAC disk unit to the 1401. [edit] Indeed you are right: 729 tape is 1958, and the first RAMAC is 1957!
However, the 729 was first introduced as a minor modification of the 727 tape drive, adding a two-gap head. The 727, in turn, was an improved version of the 726 tape drive from 1952.
Back in the 80s, when I was a computer tech, I maintained several tape stands, on a couple of different systems. However, on those, they had servo motors, so need for clutches or slip rings. They also measured the air pressure, to control the tape reels. Also, there was one occasion when a TV crew wanted to film the data centre operation and they didn't think the tape stands looked like they were working. So, we ran diagnostics to make them look busy. 🙂
It might be ancient, obsolete & nowadays a watch calculators probably millions of times faster & more memory efficient, but I was fascinated by the complexity of these wonderful pieces of engineering.So much so I want to know where I can buy one!
No, it was much more memory efficient in the 1950s than it is today.
I used drives similar to these in which the window in front of the tapes would lower for unloading and loading. We used to place the tape volumes of multi-tape master files on control box at the top of the drive. Later, the company bought STC drives, and the windows on those would raise up through the control box. It didn't take long to learn to put the to-be-used master volumes in a separate (and inconvenient) rack. So many memories seeing that printer and the 1401 control panel!
I've seen these tape drives in countless movies,TV shows, etc...Never knew they were so intricate
I had a job when I was 13 (1979) at our city municipal building, loading tapes, changing printer ribbons, and loading punched cards. the equipment was the same or very similar to that. my mother altered my birth certificate so they would hire me.
Amazing, i didn't knew how complex the tape unit was, fantastic, thank you for sharing this.
I never knew that they used clutches for the reels! Suddenly the abrupt motion makes perfect sense!
Thank you so much for your time and effort on both making these videos and keeping these amazing machines in working order. I very much look forward to your next video.
This was really cool! Thank you for this look at the workings of these!
I could watch that all day, everyday. Great work guys.
This video is a thing of beauty. Thank you for the tour. Very detailed. Excellent.
This has been a real treat to see! Thank you so much for this video, it's absolutely fascinating!
I had never considered, just how much ‘mechanical’ goes into the more modern computational rigs. And more recently even, it is not at all apparent until you try to change your ink cartridge, or even more applicable is storage devices. Mechanical engineering really is a precursor in all things electronic, to where we’d be nowhere if it weren’t for our ability to predict the mechanical implications of anything. SO AWESOME!! You know what you’re doing is important when the World wants you to film every minute of it!!
you should see 8 tape drives doing a sort! You specify the input drives, how many work drives, and the o/p drive. while 1 i/p drive was in rewind it was reading from the other. that was called phase 1, the input phase. then phase 2 was the sort phase, then finally phase 3 was the o/p phase. after phase 1 (i/p phase) you can mount scratch tapes on the two input drives, then the printer will tell you how any passes of the data has to be made to have the data in sequence before the final phase 3. simply amazing! tape sort were much faster than disk sorts too! watching the tape drives reading and writing both forwards and backwards during phase 2 was very cool.
I used to write sort exits in assembler, for the sort program. these exits can modify the data on all 3 phases.
all this was done on a machine with 16K, that's 16 thousand bytes of memory!
Absolutely. Filming a SORT7 run is on the to do list.
So many memories of watching tape sorts on 2401 drives on a 360/40. I do miss that on modern machines.
@@simonknights7526 actually tape sorts are MUCH faster than disk sorts. I used to know the programmer reslonsivle dornthe sort program and wrote tons if E15, E25 ans E35 sort exits. The sort program would constantly evaluate rhe best algorithm to use as the sort progressed. What i find amazing is that on a tape sort, you can specify the specific output drive even though it is used as a work drive as well. Also after the input phase is done, you can use the input drives as wirk drives After you mount scratch tapes on then. You could also use alt input tapes drives as well and both would be used as work drives adter the input phase. It was amazing to me that after the input phase, it would display hiw many passes of the data it would take to complete the sort.
@@rty1955 Interesting! But I don't understand how the tape sorts were faster that disk sorts - could you explain please? The first machine I worked with only had two 2311 disks (7.25MB each - one held the OS, and the other had the Fortran and Cobol compilers, and other support libraries) so could not be used for any sort work areas. When those 2311s were replaced by a number of 2314 disk drives we then switched to using the disks as work areas for sorts -because sorts were so much faster that way. But watching a tape sort was something else!
@@CuriousMarc Did you film the SORT7 tape sort? I've looked but can't find it - would be great to see!
The most interesting video I've seen in a while!! I love when people keep cool old machinery like this running.
This is one of the coolest things, I am really happy someone appreciates the antiques enough to keep them running. It's like a classic car.
Was fascinated watching these guys work on this stuff we have come such a long way
Wow. I'm blown away. I think there's as much mechanical work involved in this machine as electronic work in some modern systems. These are the days when finding bugs involved real bugs lol.
Thank you for the great video! These tape drives are what got me interested in computing originally and I miss them a lot. You all have some of the best jobs I can imagine!
This amazing machine was in operation even before robots were saying "Danger, Will Robinson!"
Thank you for uploading. I did not know 6 years. I used to use these machines in a "IBM machine room" in from 1986 to 1989 or so for me. The punch card machine is the same model. The tape machine is somewhat new model but the vacuume loading and driving mechanism is totally the same as this 1959 tape machine. Punch card machine used to run the daily batch job cards which were really bundled with rubber. and the tapes were used for daily backups out from that daily batches. If the data failure, they used for restoring the data. Still in late 1980s, they were the real and workable machines for several Japanese factories and banks or so, especially large enterprises using computer from 1960s, 70s . However I have not seen the inside at all. So this video is so valuable for me. Really great. Thanks again.
Thank you for sharing this. I have always wanted to see how such a tape drive works. Fascinating bit of machinery.
great video on the mechanics of this great machine of the era...
Brilliant work! Few things are as cool to watch as those old tape drives. Thanks for sharing a peek at the inner workings!
On your fingers, no nail Polish. I really respect that. Thank you.
The era when there was money to be made in IT!
IT technicians using lathes - brilliant.
Now technicians are on the minimum wage, sad times.
I enjoy all of your videos so much. Thank you for posting them.
Three years late into a thread, as usual, that's what the RUclips Algorithm does to me. This brings back many more memories, although I have to say, these brutes are far more complicated than the CDC machines I worked on in the mid seventies. That kit was probably mid to late sixties in origin.
The CDC's were vacuum column machines, but there the similarity ended, pretty much. The Reel Hubs were direct drive, reversible motors - quite meaty things - but none of that coaxial clutch, slip rings and fast rewind motors. I think they had five motors, including the vacuum pump. Two reel motors, the vacuum pump and the two capstan motors.
The capstan was a finely ground, forged (I think) cylinder about 75mm in diameter and a bit wider than the tape - say, 15mm? The circumference had a series of semicircular groves, not quite full width, with a hole drilled into the plenum chamber underneath. Now that I think about it, there were probably two capstans, although I just don't remember. One for forward read/write, one for reverse read/write. I'm almost sure they could do that?
So the capstan/s(?) were on either side of the read/write section and the left one hauled tape out of the supply column and the right hand one shoved tape down into the take up column. Next to the read/write head was a fixed block with holes in, which was the tape brake, also vacuum operated. They revolved at constant speed (the read/write speed) in the appropriate direction and the tape was moved by sucking it against the capstan. To stop, the vacuum was released on the plenum and applied to the brake. There was virtually no momentum because all the mass was being driven by the reel motors and controlled by the columns.
Loading a tape was very easy. You just pulled the leader off the supply reel as it hung down and pulled it across the top of the capstans, the brake and the heads and wound it on to the take up reel. Then you closed the door and hit 'LOAD'. The vacuum would come on and suck tape down both columns until they stabilised, then the tape wound forward until the EOT marker was detected. Then the READY lamp would come on and, with any luck, the deck would go online automatically and work could commence.
I have other memories about slip rings, but that was on CT Scanners and many, many years later. Thanks for a great series, Marc.
The little black plastic rollers that push the tape against the capstan to move or against fixed round rubber cylinders to stop are called prolays, one on either side.
Wow! Thank you so much for creating this video! I had never seen the inner working of machines like these. It is still amazing what people developed back in the days and it is funny to see all these young guys at work (including yourself at the lathe ;-) ) to get the machine working fine again. Thank you Marc.
Love to see that there are people that still know how to maintain these old systems.. I loved working on this sort of equipment, really well built and some amazing engineering solutions.
This is the exact kind of video needed 10 stars Marc! You have generated all kinds of hope..........
WOW you just answered so meany of my questions I had about the old tape machines! Thanks
The engineering of these machines is fascinating!
I'm shocked by how complicated the inside of that 9-Track tape machine is. In the 70's I worked at SoBel date centers in Miami and Ft Lauderdale, as part of an on-site maintenance team of three guys. We had about 40 or more Telex drives, I think they were 6450's. The reel motors were direct drive no belts, no clutches. The capstan motor, there was only one, was a permanent magnet motor with an armature that was a fiber glass disk with heavy wires bonded to it that was about 1/4 in thick and maybe 8" in diameter. The capstan wheel mounted to the armature had vacuum applied to grip the tape. It had to accelerate to full speed and write it's block of data and decelerate to stop while maintaining the about 1/2" gap between blocks of data. It had about five to six vacuum switches per tape column. And I really did love my job. All these machines were very well engineered, and were workhorses. It was great fun.
These are 7-track drives.
We need a place to send the pictures of the data centers we worked at. Tape drives at Sobel were made by Telex. When I starterd at Sobel they were using an RCA 3301 computer. I had zero IC's in it. And a lot of sketchie board contacts which were all gold plated. Core memory was in a sealed box. Used a daisy wheel printer as a console. Later changed to an modified IBM Selectric.
MANY THANKS for putting this on. Ever since I was at school in the 1960's I've wanted to know how these tape drives work. You've certainly made an older man very happy.
I never knew they sounded like that while reading and writing the tape! I knew these computers would be complex, but geez, the electronics in there are a marvel in itself.
I love IBM hardware. Magnificent stuff, thanks!
That is so freakin cool! Thank's for showing us.
This is a fantastic video. Thank you for showing us the inside of this drive!
I think it is interesting that the lathe used to make the brushes has more processing power than the 1401
Thanks for the insight.
I have aways liked the erratic movement of those old tape machines.
quite fast and advanced for the time.
How many still watch such video?? this one is awesome. thanks for the details...........you folks make thing work out interesting for us!! kudos!!
This was soo cool to watch all the way to the end. What a great demo of the tape drive that is soo cool that you got it repaired! Thank you soo much for sharing! I remember seeing these in action when I was a kid. I have a friend long been retired now that worked with these in a meat processing plant. I remember seeing them run at IBP in Dakota City. I remember my Dad as a clerk at the railroad used punch cards to keep track of train cars at Chicago Northwestern RR.
What a wonderful look into the past. Hard to imagine how far we've come since then being it wasn't that long ago.
Brilliant. I always wanted to look inside one of these units but never imagined it would be so complicated. Very interesting.
Absolutely awesome exhibit and work to get the tape drive working! Wow!
impressive engineering for its time, thanks for sharing :)
And it still works. Thanks for the awesome insides.
Wow, I saw the inside of these giants for the first time! It is like "when computers used to look like heavy machinery!"
I used to work with Teac and HP mag tape units from the 80s / 90s on Ericsson AXE10, IOG3 & IOG11, not as impressive as those units, but still rose tinted memories. That's for posting the video.
One thing I don't miss, cleaning the read/write heads. We experimented with different brands of tape, and finally bought a 'tape cleaner' that would zip the tape quickly from end to end, dragging it over a sort of 'cleaning head' so the old tapes wouldn't leave dirt on our tape drive heads.
I also used to clean tape and disk heads. The operators had a machine that cleaned the tape and also checked for wear. I also had to remind a couple of programmers to not smoke around the computers.
Absolutely beautiful machine. Love seeing it print out 2016.
Love those tape drives, they are as much mechanical as they are electronic. I remember seeing them as a kid in the early 80's and thinking how awesome they looked.
It's really fascinating to see how these drives work. Being shown the inner workings it all makes good mechanical sense - I had always vaguely wondered what sort of mechanisms were used to drive the reels and control the recoil of the tape. Never would I have imagined that there was a vacuum channel employed there!
Wow, really amazing machine, and excellent work fixing it. I would love to someday get up close and personal with a mainframe like this the way you guys do.
As a mid 90s child that used VHS tapes, seeing that fast rewind is curiously satisfying.
Thanks for this video! I ran across it while doing some research into the function of these tape drives.
Also thanks to the IBM 1401 team for the documentation on your website. The 729 CE Manual found there is newer and more informative than the version on bitsavers.
It was quite interesting to see the repair of the clutch brushes. It makes me curious about how other maintenance items are handled. There's a lot of old technology there that's going to need occasional repairs.
wow, that thing IS magnificent! bold mechanical engineering all around. congratulations, and thank you for sharing :D
Maximum respect to you guys for your time and dedication to keeping these amazing machines going.
The random movement of the reels on these drives has always fascinated me.
Thanks for sharing this.
I worked for DEC many years ago, though I'm not sure they produced a vacuum column drive. Maybe you know....?
All the best !!
these machines are built like steam trains they will last for years to the earth dies while modern computers will last 5 years and die due to the life cycle of silicone and transistors and the caps on the boards
Terrific video! Congrats on the repair.
Wonderful to see familiar old technology. "When computers looked liked computers!" and you could immediately SEE that they were working properly.
I always wondered why the units were so big compared to the size of the tape reel - very interesting!
Awesome job guys!
I'm sure no serious company on earth can reproduced the quality of these monsters now days!
(And nobody can have your talent and passion about these pieces of history)
The great "electromechanic" era.
hope to see a Silicon Graphics or Intergraph wokstation on your channel!
Best regards from France.
Wow! When computers were real MACHINES! Thanks for sharing!
Awesome technology. Thanks for sharing!
Incredible work!! RESPECT!! ⭐⭐⭐⭐⭐ Long live the old machines!! 👏👏👏👏👏💪🇺🇸
Awesome video, it gives "Mechanical drive" a new meaning. Thanks for uploading it.
Wow 20MB that must have been like 20TB back in the day, given most programs used a few KB..
I just subbed to your channel:D
Techmoan's PC.
Silver Spoon yes...
Man, I have the utmost respect for those two older gentlemen..those guys really knew what they were doing, you couldn't count on Google helping you out when something didn't work. Amazing video!
Every War Games fanatic would love to watch these old tapes going back and forth! I think Iron Eagle movie shows these as an Air force data center...
These old tape drives brings back memories, the vacuum tape drives were far better than the modern drives that were attached the AS400 computer in the early 90’s. In that day there were ancient tape drives attached to a 4381 but boy were they fast. In those days IBM built quality and I was proud to work for IBM.
This is totally mesmerizing.