Gvp 030 combo card memory mod

mjnurney

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My gvp card had 1mb ram on board. However the 030@40 or 50 had 4mb soldered to the board.

I would like to replace the ram with 4mb or 8mb if possible ?

Mike.
 
Before noticing your post, I had removed my 1MB PCB RAM and replaced it with 4MB in my GVP A2000-030 COMBO REV 3 25MHz version, but so far it has not been a great success. Here are the pictures http://relay.pp.fi/Amiga/A2000/GVP A3000-030 COMBO REV 3/ and here is how I ended up doing that:

I got the card with a faulty status.
In electronics microscope inspection I found track cut above RP4 (resistor network) in the highest running track of the PCB. The track ended to U6 MACH130 pin 73, so surely it was crucial to operation. The cut was very likely created when some object dropped over the cards top edge, because there was not just a track cut but also deep "pit" in that spot.
I repaired the cut and the card started to operate.
I bought eight NOS Hitachi HM514400CS6 chips from Ebay. These chips are 512k each so they should create 8x512k=4096k=4MB. This has 4MB and it has HM514400AS6. So I am sure I have compatible chips.
I removed the original 1MB from PCB and carefully cleaned and inspected the pads.
I then soldered the new ones and it was really painful even under electronics microscope, because the pads are a little bit offset and a lot of tracks go between the chips pins.
Then I tested and noticed the card still shows 1MB and not 4MB. I also tested installing 030 50MHz and jumpering the card for it, but no luck.
My conclusion is that the my U34-U40 chips have too "old" .JED in them and 40/50MHz card used newer .JED which enable 4MB PCB RAM.

Here are some fruits of the research I started: http://relay.pp.fi/Amiga/A2000/GVP A3000-030 COMBO REV 3/GVP A2000-030 COMBO.html

I'm planning to sell this card here on Amibay as soon as I have either solved this "problem" or given up trying.
 
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Excellent work Hanzu! (y) How were you were you able to read the PALs? As far as I could tell they were read protected. However, U6 should be readable. I will send you a PM.
 
Excellent work Hanzu! (y) How were you were you able to read the PALs? As far as I could tell they were read protected. However, U6 should be readable. I will send you a PM.

Thanks! I just read them with an Elnec programmer and it gave OK status, but so far the contents have not been tested. However they look very much the same when opened with Notepad compared to other Jedec files here: http://www.amigawiki.de/doku.php?id=en:parts:pld_download&s[]=jed I don't have free PALs to program right now. So any help on testing the contents is appreciated.

After some communication with Ralph Babel and "A4000Bear" I must conclude:

1MB PCB RAM restriction is likely to be hard-coded into the 25MHz version cards PAL set.

Even with 50MHz 030 CPU original 25MHz/40MHz cards may not be stabile in 50MHz because very likely timing and delays depend on the right set of PALs. Even original 40MHz cards do not may not run 50MHz with 50MHz 030 even though they may have same checksums in their PALs that 50MHz version cards have.

So to make this card like original 4MB & 50MHz version, a set of 50MHz version PALs or their content is required. And even this may not be all that is needed.
 
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