Where's my other FastRam?

[AmiDude]

There's a FastRAM problem with my A2500.
I've got a A2630 accelerator card with 4Mb,
and a GVP Impact A2000-HC+8 seriesII with 8MB on it.
But the system recognizes only 8MB fast instead of
12MB + 1MB chip. Where's the other 4MB fastram???
:-?
I tried different jumper settings, but can't get the
full 12MB fast-ram to work. What's wrong with it?
Anyone knows how to solve this problem?
:-?

EDIT:
B.T.W. the A2500 has the same motherboard as the A2000.
In this case rev. 6.2.

[Lemmink]

The A2630 places it`s FastRAM AFAIK in the ZII adresspace, just as the GVP-SCSI does. As the ZII adressspace is 8 MB maximum you will not be able to get more then 8 MB FastRAM until you use a "real" accelerator like a GVP G-Force, Apollo 2030 or Blizzard 2040/60.

[AmiDude]

@Lemmink

I didn't know that. What's the difference then
between the A2630 and other accelerators you
mentioned? I mean: is the A2630 not a "real"
accelerator?

 :-)

[Lemmink]

I just had a look in to hte A2630 manual and I`m right. The RAM on the card is mapped into the 8 MB adressspace.

Back then 8 MB was an enormous amount of RAM so only few would even reach that barrier due to cost of RAM alone.
What was done by more modern accelerators was that something simmilar to addmem was build into the cards ROM that assigned adresses outside of the 8 MB window to the installed RAM and tells the CPU where to find it.
The drawback of that is, that RAM outside of this 8 MB windown can not be seen directly from any ZII card, so no ZII DMA would be posisble into that RAM.
Today this "drawback" is totally neglectable as cards that use ZII DMA a re few and slow as hell anyway, plus a 030 CPU can shuffel data much faster around then any ZII DMA possibly could.
Back in the time the A2630 was made the world was a little bit different, so having the RAM in th ZII adressspace was more important then being able to add more then 8 MB to the system.

What I meant with "real" accelerator was that the A2630 is quite ancient,
having maximum 4 MB 100ns ZIP-RAM and all.
There are only two and a half reasons to use an A2630 today:

1a: You want to be as compatible as possible while having a little bit more horsepower
1b: You are a collector and want to have a real classic vintage machine with Kick 1.3, A2091, A2058 and all
2: You don`t have the money to efford a more modern accelerator :-(

[AmiDude]

@Lemmink

Thanks for explaining that. The reason why I use
an A2630 is that it was standard equiped with
the A2500. I wanted to keep the A2500 as original
as possible, and yes, I'm a collector, but I
replaced the A2091 with the GVP and I've installed
a ROM 2.05(37.500) with WB OS2.1 on the HD.

 :-)