A4000 RAM not recognized

[Pat the Cat]

Likely similar to;-

http://eab.abime.net/showthread.php?t=24348&goto=nextoldest

I have heard that memory access speed can be toggled on an A4000 between 60ns and 80ns. In software?

If so,I'd guess if you stick to 8MB 60ns fast page simms on chip RAM and alternate fast RAM slots, there's less to go wrong, You'll still be able to juggle sticks. (Although you'll still only have 2MB of chip RAM).

Anyway, if one of your double sided simms goes bad one side- it halves your 2Mb chip RAM simm into just 1mb? And makes all fast RAM vanish.

EDIT: i know, I know, most people insist you need one 2mb simm for the chip RAM. The Amiga doesn't check.

Thinking about it, maybe the reverse is also possible - if one side of your chip RAM simm goes bad, all your fast RAM goes up the swanny too.

[Pat the Cat]

Anyway, if you start by plugging in one simm (2MB or more) into the chip  RAM socket (if you have one) and then one in the top fast RAM socket, that might at least get you a booting A4000 so you can which out which sticks are faulty.

You are supposed to add them one at a time from the top, for 1-2-3 or 4 MB (if the jumper is set to 1MB simms) or 4-9-12-16 (if the jumper is set to 4MB simms).

Avoid EDO RAM. It can work, but it's usually less reliable.

If you don't have a chip RAM socket, because some A4000s just have 2MB soldered onto the board, the problem may not be with the simms at all.

EDTI: Ok, on the Edo RAM thing, some accelerator cards use them well, but generally not A4000 motherboards.

[Pat the Cat]

Correct. 1 in chip RAM plus 1 in 0,1,2,3

It makes sense to a a RAM check on each simm paired with a simm in the chip RAM socket.

The Amiga doesn't really check the whole simm, it assumes that if it can poke a few buytes and read them every so often, the whole bank is there and operating correctly.

This is why a faulty simm can seem to be working fine for a while.