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Old 20 October 2017, 12:35   #1
system11
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A2000 & A2620 RAM fallback possible?

I've read in many places that when you have an A2620 card installed, the RAM will still be available in 68000 mode.

Sysinfo says otherwise, I get the onboard 1mb chip and that's where it stops.

Does anyone know for sure? Is there something I need to do to enable it this way? The 2620 has just been upgraded to V7, made no difference. Kickstart is 1.3.

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Old 21 October 2017, 01:25   #2
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Sorry, what you read was wrong! You can't access the A2620 Fast RAM in 68000 fall back mode.

If you really want Fast RAM in 68000 fallback mode then you should get a Zorro2 memory board.
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Old 21 October 2017, 03:06   #3
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It's repeated ad nauseum on the various hardware databases, oh dear. Thanks for clearing that up it was getting quite frustrating.

Supplementary questions:

1) Does the A2630 do it (like all the sites claim) or is that more wrong information?

2) I'm planning to get a 4mb GVP scsi card (seems the best option) given that the A2630 is purchased already and somewhere in the mail. I bought a cheap Golem Ram-card for testing which also isn't here yet. If I upgraded the Golem to 4mb I'd end up with 12mb which of course isn't possible in Z2 space. I assume when active the 4mb on the 2630 will always occupy 4mb of that space. What will autoconfig do when it has a clash? It would be awesome if the golem could take over the 4mb the 2630 would present if it's disabled, while being essentially off limits when the 2630 is on. Does position in Zorro slot determine which things get to consume the ram first?

I can't find much info on the Golem, it was really just a random grab. Uses 70ns ram but I've no idea on wait states etc which are talked about with the A2058 and 8up cards.
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Old 23 October 2017, 18:21   #4
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The A2630 is really just an upgraded A2620. Sorry, but the 68000 fall back mode is functionally the same for both.

If you have 4MB of A2630 RAM configured in the 8MB of Zorro2 space, then you have 4MB remaining for Zorro2 boards. So set your RAM size jumpers accordingly and you should be OK.
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Old 24 October 2017, 22:53   #5
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Thanks for the info, I wonder why nobody gets it corrected? I contacted the owner of that amiga expansions site to let him know about the 2620, I'll send him another note.

If I deliberately put too much in, would the memory it sees last simply be unusable or cause system problems?

Example:
2630 - 4mb
GVP SCSI - 4mb
RAM board - 4mb

Would it be safe to assume the ram board if placed in the last zorro slot would simply not be used unless I disabled the 2630?
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Old 25 October 2017, 11:14   #6
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That board will be shut up if it won't fit in the address space.

I don't remember whether you will get a red expansion diagnostics screen or not, however.
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Old 27 October 2017, 19:10   #7
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Tested, works!

Installed 2630 with 4mb, GVP with 4mb and Golem ram-card with 4mb all at once. Only 8mb is available as expected and sysinfo shows which board ram is being used. It appears that the Zorro slots are autoconfigured in order - if I put the GVP last then I get 2630+Golem, if the Golem is last I get 2630+GVP.

And if I run in 68k fallback I get GVP + Golem

There's a blue message at the top on the 68k/68030 select screen about failing to autoconfigure memory, but it doesn't seem to cause any actual running problem - the RAM is just sat there unused.
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