Re: GS ram expansion

[dempson@actrix.gen.nz (David Empson)]

"Joel" <joelbuckley54.nospam.@hotmail.com> wrote:

> "Greg Andrzejewski" <pressyourluck85@yahoo.com> wrote in message
> Us6dnZzGusZHgG2gXTWcpA@comcast.com">news:Us6dnZzGusZHgG2gXTWcpA@comcast.com...
> > I'm looking to add more ram to my ROM 1 gs. Right now I have the standard
> > 1mb Apple IIgs ram expansion card 670-2500-A. What cards are available for
> > upgrading ram above 1mb? Could the chips on the card I have now be used to
> > fill an unpopulated card? Please help. Thanks.
> >
> Let me add a little to what David said.
> 
> ROM0/1 and ROM3 motherboards have different base addresses for RAM
> expansion.
> ROM0/1 starts at 256k, ROM3 at 1M.

ROM 00/01 actually starts at 128KB.  The 256KB of built in RAM consists
of "fast" banks $00 and $01, and "slow" banks $E0 and $E1.  The memory
expansion card provides additional "fast" RAM starting at bank $02, and
limited to bank $7F by the hardware and the Memory Manager toolset.  The
card can add 7.875 MB ("seven and seven eighths").

ROM 3 starts at 1 MB (bank $10) as you mentioned, but has the same limit
of bank $7F, so you can only add 7 MB of RAM via the memory expansion
slot.
-- 
David Empson
dempson@actrix.gen.nz