English Amiga Board - View Single Post - Jumper settings and advice for Alcomp A504 4meg 2meg ram expansion for A500 or A2000

snowpile79 · 26 July 2021, 16:34

Just reporting back to possibly help others with this card in the future.

As explained before there is a 4 post jumper block in the center of the card.

This info: http://amiga.resource.cx/exp/a504 is not entirely correct. I found that if you install a jumper in the top jumper block (install it across the pins horizontally) it will disable the card.

If you install a jumper on the bottom jumper block horizontally then that puts the card in 4megabyte mode (you have to populate all the chips).

If there is NO jumper on the bottom block that puts the card in 2meg mode.

At any rate I have confirmed these settings although my card wont work in 4meg mode. If I populate the top most row of ram chips the amiga yellow screens OR guru's. I believe the PAL chip that generates the CAS for that row is possibly faulty or theres another logic chip faulty. Still looking into it I'm guessing theres nobody out there who has been able to dump the PAL or even tried. It works in 2meg mode though. Anyways I'll keep poking at it.

26 July 2021, 16:34	#3
snowpile79 Registered User Join Date: Jan 2018 Location: Hancock Posts: 48	Just reporting back to possibly help others with this card in the future. As explained before there is a 4 post jumper block in the center of the card. This info: http://amiga.resource.cx/exp/a504 is not entirely correct. I found that if you install a jumper in the top jumper block (install it across the pins horizontally) it will disable the card. If you install a jumper on the bottom jumper block horizontally then that puts the card in 4megabyte mode (you have to populate all the chips). If there is NO jumper on the bottom block that puts the card in 2meg mode. At any rate I have confirmed these settings although my card wont work in 4meg mode. If I populate the top most row of ram chips the amiga yellow screens OR guru's. I believe the PAL chip that generates the CAS for that row is possibly faulty or theres another logic chip faulty. Still looking into it I'm guessing theres nobody out there who has been able to dump the PAL or even tried. It works in 2meg mode though. Anyways I'll keep poking at it.