GVP Impact A3001 memory upgrade help

[TjLaZer]

OK just pulled this old card out to install into one of my A2000's that I am restoring.  It came populated with 8 30-pin SIMMs but only shows 4MB 24-bit Fast.  Upon doing some Googling I found some jumper settings to try, remove J5 for 8MB mode.  I do it and it shows up with 8MB but hangs once WB loads!  Sooo it seems either the SIMMs are bad or the card is bad, explains why PO had it set to only 4MB.  I read this card takes special Nibble Mode SIMMs.  Problem is I cannot figure out how to remove the SIMMs on the card (without braking something)  It has a clipping method I never saw, like the SIMMs slide in and snap into place, not insert and push down to a snap like all the others.  Anyone have this card that can help?

[melange]

I have one of those, try disabling the onboard RAM on your 2000.  The Jumper J500, this will unfortunately disable the real time clock as well, but might help, worth a try :-)
It disables the 512K RAM at $C00000.

See if it hangs still.

[melange]

Just looked at the Jumpers for the A3001 and it says for 8MB that Ram slots CN3 through to CN10 should all be populated and J5 ON.

And it (8MB of 1M simms) is not supported if you have a 50mhz processor.

Just looked at that again, and I had it wrong, CN3-CN10 are of course Ram slots not Jumpers corrected above statement.

looks like you've done the right thing, but there are a lot of Jumpers to do with clock speed, and seeing as the setup your trying to use isn't supported by 50mhz processor, I'd check all jumpers associated with clock speed and ensure you have them set correct.

[TjLaZer]

Yeah J5 is the jumper for 8MB, but it seems the SIMMs that are installed are probably not compatible.  Problem is I cannot seem to remove them!  Real pain and I dont want to break the tabs.  It's a spare machine so 4MB is fine for now I guess.  My other 030 card a A2630 only has 2MB on it so this one is preferred.

[melange]

Apparently the A3001 is also compatible with special UNIX Boot ROMs as found on the Commodore A2620 or A2630.  I've never been able to locate the ROM code, or I'd give it a try, just for the hell of it. :-)

[alexh]

Are you sure that the simms are just not 512kbyte simms?

8 * 512 = 4Mbyte

If you fool the card to reporting more RAM than the simms hold it will work for a short time and then crash as soon as an address that doesnt exist is accessed.

[melange]

The card uses special GVP 30pin Simms if I remember correctly.  Not many compatible types around from what I have read.