Re: RAM CARDS for IIGS

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

In article <Pine.OSF.3.91.950724151559.16514A-100000@unicorn.it.wsu.edu>,
Sedgwick  <sedgwick@wsunix.wsu.edu> wrote:
> I was interested in the AE RAMKEEPER because you could put 2 8meg RAM
> Cards on it and expand your IIGS to 16megs of RAM with leaving Slot 7
> open for a SCSI card. 

That can't be right.  The IIgs won't support more than 8MB of fast
RAM.  The memory manager only supports fast RAM in banks $7F and
lower.  There might also be hardware reasons why banks $80 to $DF
cannot be used.

You certainly couldn't use 16MB - banks $E0, $E1 and $F0 up are
already used.

> I am also interested in hearing from people who own or have 
> owned Octoram cards, GSJUICE, and GSSauce cards.

I have an OctoRAM (4 MB) in my ROM 1, and a GS Juice Plus (4 MB) in my
ROM 3.  No problem with either of them in this configuration.

The OctoRAM supports 1, 2, 4 or 8 SIMMs, either 256K or 1MB (all must
be the same size).  It is not DMA compatible with 8 SIMMs installed,
but works fine with 1, 2 or 4 SIMMs.

I haven't tried using it in the ROM 3, but it should work fine.  I did
a partial circuit analysis on it to see how it works, and the only
addressing trick it pulls is to use one of the bank address bits on
the data bus to decode the address when 8 SIMMs are used.  (This is
probably the most common method of supporting more than 4 MB on a RAM
card, and is not DMA compatible except with a RamFast.) The same
method should work on a ROM 1 or ROM 3.  It should also be possible to
use seven 1MB SIMMs in a ROM 3 to get a total of 8 MB (the 8th SIMM,
if present, is not usable in a ROM 3).  I'm not sure which SIMM is the
one that could be removed, and I haven't tried it.

I also have the add-on "OctoRAM ESP" card, which is a piggy-back static
RAM card that implements a ROM disk of up to 512K.  I retired this card
and removed its RAM when I got a hard drive, as it isn't really large
enough to be useful.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand