jgallego@pnet01.cts.com (Jose Gallego) (05/23/91)
This is the result of the comments I received regarding the modification of
the A500 with Rev. 6A board:
1. You can add 4 extra memory chips to those empty sockets. You can do this
by either soldering the chip to the motherboard or solder chip sockets and
then plug in the chips.
2. You need to cut the trace on jumper JP2. This is locate to the left of the
68000 around the middle. This jumper is located between the 68000 and the ROM
(U6).
3. You need to solder the trace in jumper JP2 to the middle to the bottom.
This change (step 2 and 3) selects your A501-type memory expansion to be used
as chip ram.
4. Find jumper JP7A, locate near the A501 memory expansion and cut the trace.
This "should" work. I have not yet tried it. Will this leave me with 1Meg of
chip ram and 512K of fast ram????
One final comment that I received: THIS MODIFICATION IS NOT APPROVED BY
COMMODORE AND VOIDS YOUR WARRANTY... (neither do I, since I haven't tried it).
I am not sure what does removing the JP7A does, is this suppose to disable the
A501?
Thanks to those that answer my question,
Jose
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PHONE:(619)477-2024s8922967@ipc05.mqcs.mq.oz.au (Murray John GILBERT) (05/23/91)
adding an extra 4 memory chips to those empty sockets sounds good. I've considered doing it and also wondered as you seem to have about whether we would then have 1megchip + 512K slowfast or 512K chip + 1meg slowfast or just 512K of each. I have another question to add: I heard about six months to a year ago that these four 256kx4 chips on the rev 6a motherboard a500 could be replaced by four 1Mx4 chips and the agnn Agnus 8372a (which I have) be swapped for a 8372b which the 3000 has? Once the appropriate jumpers are change then there would be 2MB of chip memory. I am wondering: will the 6a 500 take the 8372b, I thought that its pinout configuration was a bit different to make 2MB possible (same silicon inside the package though as the a), are the places where the 256kx4s are compatible with the 1Mx4 chips. And lastly, by analogy with Jose's idea of using the other four places could I have 4Meg on the motherboard if I put 1Mx4s in all the 8 chip places ( even though only 2MB could be chip at most ) Also who in Oz, in Sydney, Northern Beaches preferably knows about the 2MB chip mod, Hard Disk Cafe maybe? Thanx, Murray