Re: //gs Memory 8 or 16megs?

[marvinmiller@hotmail.com (Marvin Miller)]

Is there any way to 'fix' the memory restrictions in a //GS or is it
just not possible to make it use the full 16 megs?

Assuming it could be fixed, would anything be able to use it? My hopes
were to have a 16 meg unit with a 8 meg ram disk - but after seeing
the posts on the hardware limitations, it looks like it's not worth
it.

BTW David & all, thanks for the answers previous. I printed them out
and they make road mapping my hardware choices much easier.

Best;
Marvin

On Wed, 25 Oct 2000 22:40:07 +1300, dempson@actrix.gen.nz (David
Empson) wrote:

>Roger Johnstone <rojaws@es.co.nz> wrote:
>
>> Bernie to the Rescue has an option to allow the emulated IIgs system to have
>> up to 14MB of RAM. The OS and programs will happily use this memory. I think
>> the 8MB restriction in a real GS is only in the hardware, not the firmware,
>> since even the CDA control panel sees the entire memory and will let you set
>> up a RAM disk larger than 8MB.
>
>There are two restrictions:
>
>1. The hardware only regards banks $00 to $7F as being "fast RAM".
>Anything above that are either "slow RAM" ($E0 and $E1), "ROM" ($F0 or
>higher) or "nothing" ($80 to $DF and $E2 to $EF).  The necessary
>addressing signals are not provided to the memory expansion slot in the
>"nothing" areas, so a memory expansion card cannot use these areas.
>
>(The TransWarp GS gets around this: it has some extra ROM somewhere in
>the $D0-$DF area, but it can do this because it has first crack at
>decoding addresses from the processor, before they get to the
>motherboard hardware.)
>
>2. The Memory Manager toolset (in ROM) assumes that the fast RAM in the
>IIgs doesn't extend past bank $7F.  It would be necessary to patch the
>firmware to allow the memory to extend beyond this point.  There is
>nothing stopping an emulator from doing this.  (14 MB would be all of
>banks $00 to $DF.)
>
>Every other piece of software depends on the Memory Manager for
>determining memory limits, so the RAM Disk configuration should
>automatically be able to use more than 8 MB if you had a patched memory
>manager.