Re: Sirius Ram and ROM 00 Question . . . .

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

<hubble1@my-dejanews.com> wrote:

> I have an older GS which boots up with a ROM 01 message, but
> it only has 256K of built-in RAM.  Is this what I have heard
> referred to as a ROM 00 GS?

No.  A ROM 0 IIgs doesn't display any copyright message or ROM version
on the startup text screen - just "Apple IIgs" at the top.

ROM 0 is the original firmware that was shipped with the IIgs in
September 1986.  ROM 01 was available as an upgrade (single ROM swap) in
1987, and machines from then until 1989 were shipped with ROM 01
preinstalled.  (After 1989 came the 1 MB motherboard, which contains ROM
version 3.)

> Also, I recently purchased a Sirius RAM card with 8 megs.
> There is a dip switch setting to choose between "1024K" and
> "256K".

That will be to select the size of SIMMs which are installed on the card
itself.   The OctoRAM card (which I have in my ROM 1) has a similar
setting.  It has nothing to do with the amount of RAM on the
motherboard.

Assuming the Sirius card supports the same configurations as the
OctoRAM, you should be able to install 1, 2, 4 or 8 of the same type of
SIMM: all must be 256KB, or all must be 1MB, and the size jumper must be
set accordingly.

If you have eight 1MB SIMMs installed on the card, this jumper must be
set to the 1024K position.

> Setting up the dip switches for 1024K and 8 megs on the card resulted in
> the system hanging just prior to reaching the finder when booting a GS/OS
> 6.0.1 floppy.

This is the correct setting, so it sounds like a fault with your
motherboard, with the memory card, or perhaps one or more of the SIMMs
installed on it.

> Is my particular GS ROM incapable of supporting more than
> 2 megs of additional RAM?

Every version of the IIgs motherboard (and firmware) can support 4MB of
expansion RAM without the card doing anything special.

To support more than 4MB requires the card to cheat a little, but it
works fine for everything except I/O cards which use Direct Memory
Access.  (Even then, the RamFAST SCSI card is able to use DMA with most
8MB RAM cards.)

The absolute limit is 8MB of "fast" RAM, including the motherboard RAM.
This means that with a ROM 0 or 01 IIgs, an 8MB RAM card will have 128KB
of "wasted" memory on the card, while a ROM 3 IIgs with an 8MB RAM card
will have 1MB "wasted".

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