FYI, there is a luma signal on the RGBi connector, so if you make a cable with an rca connector from pin 1 (gnd) and pin 7 (luma), you can just plug it into a composite monitor and have monochrome 80 column display, no rgb monitor necessary!
Yes! Commodore actually made that cable. The extra green monochrome input on the 1802 monitor sold alongside the C64C in the late '80s was intended for C128 users on a budget. ☺️ -- JC
I had never heard that that VDC RAM upgrade was common at all. My family under my parents, and then just I, have had a Commodore 128 (regular) since 1988, and I wish I had known about, and we had had the willingness to spend the money on, and the capability of installing, as well as software that would have taken advantage of, the VDC RAM upgrade, because I just read somewhere that having that extra RAM enabled even higher resolutions than normal. Although where I read didn't teach how to get into those modes or what error messages we may have gotten while trying to switch into them without the upgrade. All these decades I really never knew about that until just this recent time when I read about that a little bit! But if I find some software that really does take advantage of that upgrade, then I would be willing to do it nowadays.
Interesting! Your population sample seems to defy what I understood to be the less-than-stellar popularity of the 128 vs the 64, even though it sold well in its own right. Also, if you're *THE* Bo Zimerman, welcome! 😎 -- JC
@@BasicBitesCA Thanks for the welcome! This was around 1987-1992 btw, and well, I realize my experience is not exactly a scientific sample, but it was what it was. :) I had 5 friends with computers, and 4 of them had 128s or 128ds.
Exactly! 🤷♂ Oh well. I don't consider too much of the time wasted, because as much as I hate de-soldering ICs, I appreciated an excuse to upgrade the VDC RAM. 😎
Good, I like your reasoning about using the ARM SID in there. Now how would you go about programming a 128/64 to switch that chip's modes in software even though it was never designed to do such a thing? How would the software get access to the switchability of the chip?
Do those two video chips have the same number of pins? Because if they do, and if the Vcc and ground are in the same places, then will you please make a video showing us what happens with the computer switched to both modes when you swap them?
Why does the VIC-II chip depend on system RAM instead of being given its own RAM? Conversely, why does the VDC get to have its own RAM rather than also sharing system RAM?
Hey JC thanks for this video. my C128's 80 column screen is starting to experience some issues, So, I'm gathering up the chips & parts I will need for the fix. Can you confirm that the logic chip is a 74LS244? also what are the values on those caps? thanks for you help!
My pleasure! I hope your issue doesn't turn out to be the VDC itself. The exact logic chips I ordered were SN74LS244N. For the capacitors, I highly recommend downloading either or both copies of the C-128 Service Manual linked to in the description; it has all of the cap types and values by location on the PCB. Good luck! -- JC
@@BasicBitesCA Thanks, I'll take a look at the C128's service manuals for the caps. I actually have a 'presumed working' spare VDC chip so hopefully I should be ok.
You should ALWAYS check the voltage rails first, then the clock circuitry, when dealing with ANY kind of clocked circuit like this computer. These are easy to check,
But the Commodore 128 actually _does_ have a REAL Commodore 64. It has all of the circuitry necessary to function as a bit-by-bit discrete 64 (even though the CPU, VIC-II chip, and SID are updated versions; and with only very minor compatibility issues, which different discrete 64 revisions have between each other anyway).
The SID is exactly the same, and the VIC-IIe is also basically the same, but adds a couple extra pins to handle signals for new keys and the Z80. The 8502 CPU is the only real upgrade, as it can run at 2 MHz when the VIC video output is disabled (which is also possible in C64 mode!).
It's an Abracon oscillator, DigiKey part number 535-9207-5-ND. I imagine any reputably-sourced 16Mhz oscillator in the standard full size form factor would work just fine. -- JC
❤️ Love the initiative ❤️ - subscribed, shagged and bagged. Just, plelelelelelase (Roger Rabbit voice) don't be shy with the C128 stuff. There really is not enough Commodore "Chimera" 128 content out there in this vast ocean of C64 dominance. - You obviously needed to check the RAM ICs. But there does exist a modern daughterboard upgrade for the VDC, which ignores the onboard 16K RAM and replaces them with the full 64K. Almost bringing a wedge C128 up to D/DCR specs. Only just almost, because you still have to replace the Basic 7 ROM with the 318018-04 and 318019-04 (16K ROMs) wedge/D versions of the bug-fixed 318022-02 (32K ROM) DCR version... and of course popping a Basic 8 ROM in the U36 socket, for more in-Basic VDC graphics support doesn't hurt. - Although I am pretty sure this daughterboard won't fit with the onboard DRAMs socketed. But it's not really a biggie, because you can just leave the socket empty, maybe covered with a bit of electrical tape to avoid any potential shorts. Obviously not needed, if you can just pop in two 32K RAM ICs in those sockets (I haven't tried that).
Thank you very much! I have no reservations about posting additional C128 content, and look forward to doing so. ☺ The mainstay of Basic Bites is the good old C64 according to my own interests/experiences, but I intend for the C128 to continue being a secondary topic. The machine always intrigued me (and I now *finally* own a couple)! Regarding the VDC RAM: the "drop-in" upgrade that I'm familiar with is the SaRuMan by eslapion, which simply sits between the VDC and its socket, thus bypassing the RAM chips on the board completely. However, it's the height of a socket... I'm doubtful that the metal box would close with it in place, and I'm not a fan of pitching out the shields and gluing heatsinks to the chips. If I had one around, though, I would have used it in testing. -- JC
@@BasicBitesCA I think the ones I have are SaRuMan's as well. That 'in-between" part is what makes me call them daughterboards. I don't have the metal lit on in any of my 3 C128s anymore. I don't even have the metal cover shielding on anymore either. Simply because of all the multi-ROM daughterboards I've crammed in there, which elevates my replacement EPROMs to a point where it just becomes impractical. It ends up being a choice of either one or the other, "you" can't have both. The SIDFX (dual SID) daughterboards, I have in 2 of them, does the same. So, I must confess to putting on some small heatsinks on all the harder-to-replace MOS chips instead. Several per chip actually, although not glued. It is the same kind "you" would use on a Raspberry PI, so with easily removable heat conducting tape. - Besides doubling as a heatsink the shield really isn't needed and was only required to meet the regulation standards of that era. Some argue that it protects the C64/C128s from outside interference. But the concern at the time was really the other way around and it doesn't at all protect the internal components from interfering with each other. And there is plenty of that going on, especially with the older breadbin longboards. - Anyway, in case you are wondering; that SIDFX board is a Danish product (I'm from Denmark) which takes all the "danger" out of installing dual SIDs. You can even put a 6581 in back-to-back with a 8580 without changing components or setting any jumpers. The circuitry just automatically detects what you put in and takes good care of our precious SIDs for us. It comes with C64 configuration software which makes you able to change exactly how the two SIDs are stereo-duetting practically on the fly.
@@BasicBitesCA If you'd like to check out how it sounds, I made a small RUclips video some years back called "The Great Giana Sisters Intro Tune on a C128 with Dual SIDs' as an attempt to visualize the slight stereo effect you can get from a 6581r4AR and a 8580r5 duetting in dual-mono (one SID in the left speaker and the other in the right).
@@Zhixalom I don't think the SaRuMan would physically interfere with the VDC RAM chips (socketed or not), as its footprint is the same as the VDC. Heatsinking and a general appreciation for keeping retro-computers more-or-less in factory condition are the main reasons why I have all of my (metal) shields in place. -- JC
FYI, there is a luma signal on the RGBi connector, so if you make a cable with an rca connector from pin 1 (gnd) and pin 7 (luma), you can just plug it into a composite monitor and have monochrome 80 column display, no rgb monitor necessary!
Yes! Commodore actually made that cable. The extra green monochrome input on the 1802 monitor sold alongside the C64C in the late '80s was intended for C128 users on a budget. ☺️ -- JC
Congratulations on your repair!
I had never heard that that VDC RAM upgrade was common at all. My family under my parents, and then just I, have had a Commodore 128 (regular) since 1988, and I wish I had known about, and we had had the willingness to spend the money on, and the capability of installing, as well as software that would have taken advantage of, the VDC RAM upgrade, because I just read somewhere that having that extra RAM enabled even higher resolutions than normal. Although where I read didn't teach how to get into those modes or what error messages we may have gotten while trying to switch into them without the upgrade. All these decades I really never knew about that until just this recent time when I read about that a little bit! But if I find some software that really does take advantage of that upgrade, then I would be willing to do it nowadays.
All my friends with computers, save one 64 owner, had C128s or C128Ds in the late 1980s.
Interesting! Your population sample seems to defy what I understood to be the less-than-stellar popularity of the 128 vs the 64, even though it sold well in its own right. Also, if you're *THE* Bo Zimerman, welcome! 😎 -- JC
@@BasicBitesCA Thanks for the welcome! This was around 1987-1992 btw, and well, I realize my experience is not exactly a scientific sample, but it was what it was. :) I had 5 friends with computers, and 4 of them had 128s or 128ds.
I was sitting here the whole time saying to myself... you know, it's never the crystal, but I bet it's the crystal. 🤣
Exactly! 🤷♂ Oh well. I don't consider too much of the time wasted, because as much as I hate de-soldering ICs, I appreciated an excuse to upgrade the VDC RAM. 😎
"...Routed by that logic chip.... MY logic was therefore..." "Logically..."
Haha, nice puns!
Like Adrian always says, "always check the voltages and clock first when troubleshooting old computers." That would have saved you a lot of trouble...
VDC 80 column is sharp as a tack!
"Cyndrilical"? What's that? Were you trying to say _"cylindrical"_ instead?
Good, I like your reasoning about using the ARM SID in there. Now how would you go about programming a 128/64 to switch that chip's modes in software even though it was never designed to do such a thing? How would the software get access to the switchability of the chip?
Do those two video chips have the same number of pins? Because if they do, and if the Vcc and ground are in the same places, then will you please make a video showing us what happens with the computer switched to both modes when you swap them?
Why does the VIC-II chip depend on system RAM instead of being given its own RAM? Conversely, why does the VDC get to have its own RAM rather than also sharing system RAM?
Hey JC thanks for this video. my C128's 80 column screen is starting to experience some issues, So, I'm gathering up the chips & parts I will need for the fix. Can you confirm that the logic chip is a 74LS244? also what are the values on those caps? thanks for you help!
My pleasure! I hope your issue doesn't turn out to be the VDC itself. The exact logic chips I ordered were SN74LS244N. For the capacitors, I highly recommend downloading either or both copies of the C-128 Service Manual linked to in the description; it has all of the cap types and values by location on the PCB. Good luck! -- JC
@@BasicBitesCA Thanks, I'll take a look at the C128's service manuals for the caps. I actually have a 'presumed working' spare VDC chip so hopefully I should be ok.
You should ALWAYS check the voltage rails first, then the clock circuitry, when dealing with ANY kind of clocked circuit like this computer. These are easy to check,
Voltages were known to be fine going in. This was a fully functional C128, with the exception of the VDC sub-system. -- JC
Excellent and subscribed!
Thank you and welcome! -- JC
But the Commodore 128 actually _does_ have a REAL Commodore 64. It has all of the circuitry necessary to function as a bit-by-bit discrete 64 (even though the CPU, VIC-II chip, and SID are updated versions; and with only very minor compatibility issues, which different discrete 64 revisions have between each other anyway).
The SID is exactly the same, and the VIC-IIe is also basically the same, but adds a couple extra pins to handle signals for new keys and the Z80. The 8502 CPU is the only real upgrade, as it can run at 2 MHz when the VIC video output is disabled (which is also possible in C64 mode!).
@@dans.8198: Yep, except that the SID actually is a bit of a different version.
(Also, I edited "real" into "discrete," since both are real.)
@@HelloKittyFanMan SID is identical. It is either the 6581 (12V version) or the 8580 (9V version). Both were used in the C64.
@@dans.8198: Then they're _not_ identical.
Do you know the part number of the new oscillator you used?
It's an Abracon oscillator, DigiKey part number 535-9207-5-ND. I imagine any reputably-sourced 16Mhz oscillator in the standard full size form factor would work just fine. -- JC
❤️ Love the initiative ❤️ - subscribed, shagged and bagged. Just, plelelelelelase (Roger Rabbit voice) don't be shy with the C128 stuff. There really is not enough Commodore "Chimera" 128 content out there in this vast ocean of C64 dominance.
- You obviously needed to check the RAM ICs. But there does exist a modern daughterboard upgrade for the VDC, which ignores the onboard 16K RAM and replaces them with the full 64K. Almost bringing a wedge C128 up to D/DCR specs. Only just almost, because you still have to replace the Basic 7 ROM with the 318018-04 and 318019-04 (16K ROMs) wedge/D versions of the bug-fixed 318022-02 (32K ROM) DCR version... and of course popping a Basic 8 ROM in the U36 socket, for more in-Basic VDC graphics support doesn't hurt.
- Although I am pretty sure this daughterboard won't fit with the onboard DRAMs socketed. But it's not really a biggie, because you can just leave the socket empty, maybe covered with a bit of electrical tape to avoid any potential shorts. Obviously not needed, if you can just pop in two 32K RAM ICs in those sockets (I haven't tried that).
Thank you very much! I have no reservations about posting additional C128 content, and look forward to doing so. ☺ The mainstay of Basic Bites is the good old C64 according to my own interests/experiences, but I intend for the C128 to continue being a secondary topic. The machine always intrigued me (and I now *finally* own a couple)! Regarding the VDC RAM: the "drop-in" upgrade that I'm familiar with is the SaRuMan by eslapion, which simply sits between the VDC and its socket, thus bypassing the RAM chips on the board completely. However, it's the height of a socket... I'm doubtful that the metal box would close with it in place, and I'm not a fan of pitching out the shields and gluing heatsinks to the chips. If I had one around, though, I would have used it in testing. -- JC
@@BasicBitesCA I think the ones I have are SaRuMan's as well. That 'in-between" part is what makes me call them daughterboards. I don't have the metal lit on in any of my 3 C128s anymore. I don't even have the metal cover shielding on anymore either. Simply because of all the multi-ROM daughterboards I've crammed in there, which elevates my replacement EPROMs to a point where it just becomes impractical. It ends up being a choice of either one or the other, "you" can't have both. The SIDFX (dual SID) daughterboards, I have in 2 of them, does the same. So, I must confess to putting on some small heatsinks on all the harder-to-replace MOS chips instead. Several per chip actually, although not glued. It is the same kind "you" would use on a Raspberry PI, so with easily removable heat conducting tape.
- Besides doubling as a heatsink the shield really isn't needed and was only required to meet the regulation standards of that era. Some argue that it protects the C64/C128s from outside interference. But the concern at the time was really the other way around and it doesn't at all protect the internal components from interfering with each other. And there is plenty of that going on, especially with the older breadbin longboards.
- Anyway, in case you are wondering; that SIDFX board is a Danish product (I'm from Denmark) which takes all the "danger" out of installing dual SIDs. You can even put a 6581 in back-to-back with a 8580 without changing components or setting any jumpers. The circuitry just automatically detects what you put in and takes good care of our precious SIDs for us. It comes with C64 configuration software which makes you able to change exactly how the two SIDs are stereo-duetting practically on the fly.
@@BasicBitesCA If you'd like to check out how it sounds, I made a small RUclips video some years back called "The Great Giana Sisters Intro Tune on a C128 with Dual SIDs' as an attempt to visualize the slight stereo effect you can get from a 6581r4AR and a 8580r5 duetting in dual-mono (one SID in the left speaker and the other in the right).
@@Zhixalom I don't think the SaRuMan would physically interfere with the VDC RAM chips (socketed or not), as its footprint is the same as the VDC. Heatsinking and a general appreciation for keeping retro-computers more-or-less in factory condition are the main reasons why I have all of my (metal) shields in place. -- JC
@@Zhixalom I will check out your dual SID video! -- JC
Is there a way that you could make these videos without being kind of shouty about it?
"Also... as well..."? Heheh, oops.
* All of the 35-year-old _electrolytic_ capacitors.