Commodore 128 RAM repair, VDC memory upgrade and 32k ROM mods.
ฝัง
- เผยแพร่เมื่อ 9 ก.พ. 2025
- Hello all...
Here's my first dive into a C128. Just a simple RAM repair followed by the 64k VDC memory upgrade and some Kernal and BASIC ROM upgrades. This all may be common knowledge to seasoned C128 users and techs but hopefully this will help other noobs like myself.
This is part 1 of probably 3 that I'll be posting. Next will be some more U36 option rom stuff then finally some video output stuff when the rest of the parts arrive.
32k ROM conversion reference:
www.rift.dk/up...
This is a fantastic video. Best one I've seen for an overview of essential c128 updates
Glad it was helpful!
Excellent video. Excellent narrative and video content. A+++++++.
Glad you enjoyed it!
When someone has the ability to rattle off chip numbers….. it tells me this guy knows what he’s talking about… to say the least.
Good video. I'm sure your video's will get better over time!! Keep up the work with the C128's
Thanks 👍
Nice video. Good job.
Instead of stealing a C64's memory, you can use Saruman-VDC to upgrade your VDC RAM.
That's a very good solution too, but I'm cheap and the 64 was readily available. I've since replenished my supply of 41464 chips so everything is whole again.
@@retrotechinsanity There's also the power argument. A pair of 41464 will consume about 60mA on the 5Vdc source. Saruman-VDC uses a modern ultra low power static RAM chip which draws 5mA.
Nice. If you have a tv with composite input you can wire up the 9pin 80 col connector to do monochrome 80 col out just to see if its working. its pin 7 for signal and pin 1 or 2 for ground.
Yep, wait till ya see my next 128 video... Modded a 2nd one on the cheap...
@@retrotechinsanity lol, forgot I was a month late to this party. watching the next videos now.
@@timpsensky5181 There will be a 4th video (not done yet) with a poor mans 80 column mod on another machine.
You didn't say what diagnostic rom file you used. I see there are several depending on the diagnostic test hardness one has. I have two test harnesses for the '64. I was guessing that it would work on a 128 (with the exception of the 128DCR - because of the cassette edge connector being on the side and the opening too small to plus in to??).
Dang, the only EEPROMs I have right now are 74C512, which means I have to load an 8K .bin file on it 8 times? It won't work if the program is only burned on it once?
Pretty sure i got the bin file for the ROM from zimmers.net. I wind up using oversized ROM chips all the time too, seems like a waste but they're cheap enough so whatever...
@@retrotechinsanity I have two ROM boards, a 1541 Diagnostic Card PCB and a VersaCart PCB. I have a 1541 Alignment ROM image (8K) that I can get to boot on both boards. I've tried a W27C512 with 8 concatenated 8K images of the 1541 Rom Image and that ROM will boot on both boards.
I have yet to get an 8K Diagnostic ROM image to boot, either in an 8K EPROM (27C64), or concatenated 8 times in to a 27C512.
I am getting very frustrated. I can not download and image from zimmers that seems to work, or the Commodore Software site. I am not sure what I am doing wrong.
Hi. Just found this video. Thank you for all the good info. I'm working on my C128 and was having video problems. Was wondering if you could burn me a copy of the diag chip. I would greatly appreciate it. Thank you.
I could, but it would probably be cost and time prohibitive for me to send it. I live in the middle of nowhere.
This is a great video. I have kept your video saved as a guide for a while now. I finally purchased JiffyDOS myself. I have found that basic.390393-01.bin is the inverted version of the 128D/DCR basic.318022-02.bin. I assume it was a factory created upgrade for the C128 Flat. I am going to use it so I can just close J4.
you put JiffyDos in your 128 is your Driver switcher working when you hit Control + D??????? mine is not!
Actually no it doesn't in 128 mode. Kinda pisses me off! I haven't gotten around to figuring out why yet though.
You Can use 010 or 020 rom's and make 4 or 8 different kernels...it will require 2 switches.
How useful is VDP memory upgrade?
There's a few demos that take advantage of it. It also comes in handy using Novaterm / Striketerm as you can use the VDC as a 64k buffer for data when using 40 column mode.
Where did you get that rom chip?
Those are just Winbond 27c512 chips. Got them from Aliexpress.
I am troubleshooting a c128. Black screen on boot. Would that diag chip help? How much would you charge to burn and send me one? And maybe a set of the new roms too? I don't have a programmer.
There is a possibility it could help, but black screen could mean the MMU or PLA is bad then none of the diagnostic ROMs would boot either. Also I've seen a bad kernal rom drag down the entire data bus, so that's a possibility too. I can certainly burn you a chip for cheap, hopefully you're in the US so shipping would be cheap too. What's the best way to contact you directly?
@@retrotechinsanity I replaced the pla and kernel rom. Email me, ill give you more info on what it's doing.
@@musicdad I don't see an email address in your about page. you can shoot me one... insanity at hellbent dot cc
Which one is the CP/M ROM?
Don’t need a rom for that just boot CPM from disk and the 128 will go into z80 mode
@@MarianoLu My 128 had CP/M in the firmware...not on disk. There was a button on the back of the case that you held down during boot and it would boot into CP/M on the z80B processor at 2MHz. It changes the clock speed. The 128 did not automatically come with a floppy disk drive, but CP/M was available.
I really think the C64 bootup screen looks better than the 128.