C-128 VDC RAM Upgrade

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motrucker
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C-128 VDC RAM Upgrade

Post by motrucker » Sun Jul 26, 2015 7:55 pm

Has anyone here added the VDC RAM Upgrade to their C-128? It makes the flat 128 perform like the C-128DCR, since it ups the VDC RAM from 16Kb to 64Kb. There is a neat no solder solution:
http://www.ebay.com/itm/Commodore-128-6 ... 58b47c12ed
I can add that I have dealt with this seller before. He goes under the avatar of boulderdash, and is well known in the Commodore comunity. You will not find a better ebay seller.


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Borat
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Re: C-128 VDC RAM Upgrade

Post by Borat » Tue Jul 05, 2016 12:15 am

So this is the mother of necro-posts... well there is only one other post in the thread :P

I just bought a 64K VDC upgrade but unfortunately it isn't working. The characters on the 80 column boot screen are messed up. If I remove the plug-in board and go back to the standard setup - all is OK. I contacted the UK ebay seller (very reputable) and he has sent me a replacement to try (arriving tomorrow hopefully).

I didn't realise it was as easy as replacing the 2 RAM chips on the main board or I would have done that quite a while ago, but I'm not really a C128 guy (yet).


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Re: C-128 VDC RAM Upgrade

Post by Borat » Sun Dec 11, 2016 1:49 am

Apologies for yet again necro-bumping this thread. I complete forgot to update it as to the solution....

There was a tiny solder bridge under the socket, between it and the PCB. I only found it by using my DMM to test continuity between each socket pin and its neighbour. Soon found the short.

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Re: C-128 VDC RAM Upgrade

Post by eslapion » Sun Dec 11, 2016 5:45 am

I vaguely remember there was a few small software that can check the exact amount of VDC RAM you have installed. Would you have a link ?
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Re: C-128 VDC RAM Upgrade

Post by motrucker » Sun Dec 11, 2016 11:01 pm

There is another potential problem with these boards. I have an old PCB made by Chip Level Designs that has such short pins that pressure must be applied to make it work (contact). I had to resort to a cable tie to keep it down, before I finally just replaced it.
All in all, it's most likely easier to just change the RAM chips.

@ eslapion
I can't find the program I used to use, but I found this routine on another site that should work:
"Type this line in 80 column mode:

POKE DEC("D600"),28:POKE DEC("D601"),63:SYS DEC("FF62"):SCNCLR <RETURN>

If the screen looks normal and says READY, and all that, you've got 64K
display memory. If the screen is full of 0's and looks like a programming
nightmare, you've got 16K (just hit Stop/Restore and let Mr. Kernel fix it).

My 128 isn't set up right now, so I can't verify this.
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Re: C-128 VDC RAM Upgrade

Post by Borat » Thu Dec 15, 2016 11:10 pm

I actually removed the board motrucker, because it didn't appear to be secure enough. I ended up upgrading the video RAM chips on the board instead. Much better solution.

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Re: C-128 VDC RAM Upgrade

Post by motrucker » Fri Dec 16, 2016 1:22 am

Borat wrote:I actually removed the board motrucker, because it didn't appear to be secure enough. I ended up upgrading the video RAM chips on the board instead. Much better solution.
I absolutely agree. The problem with some of the "no solder" boards is that the pins are to short. I had to use a nylon cable tie to keep pressure on the damned thing. I know of one board made here in the U.S. that has long enough pins, but I bought a board from Chip Level Designs years ago - just finally used it. Some time in the near future I will most likely put in the larger RAM chips.
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