Re: IIGS rom3/rom1 board differences

["myoldmac.net" <usenet@myoldmac.net>]

Jon wrote:
> Is there something different about rom3 and rom1 machines
> (which I assumed was what was described in the schematics)?  Is there
> something missing from my board (jumper?) Anyway I have got it working
> by soldering the broken links with wire wrap wire (hidden under the
> board) I'm just curious what could've caused this.

Dear Jon

Released in September 1986, the original GS ROM 00 (which tended to
have the Woz signature on the front case, though that is no guarantee)
must have one or two chips (the ROM and possibly also the Video
graphics controller) upgraded to become a ROM 01 machine and boot/run
current software.

A later revision of the motherboard, known as the ROM 3 had a number of
significant changes: more ROM (256K vs 128K) on the motherboard, more
(1MB vs 256K) RAM on the motherboard, different capabilities for the
internal slots, better support for the disabled, and a cleaner
motherboard which can result in quieter sound support.

The extra ROM allows more parts of the system software to be accessed
from there, which allows a ROM 3 to boot and run GS/OS and GS/OS
programs slightly faster than a ROM 01. (The two have identical toolbox
functionality from the programmer's standpoint, however.)

To determine which ROM version you're using, when you power it up, it
should say "Apple IIGS" at the top of the text screen for a second or
so, and possibly some text at the bottom, which states either ROM 01 or
ROM 3. If it does not say either, you have a ROM 00, the original
version. You must upgrade a ROM 00 to a ROM 01 (easy-- swap 2 chips),
or a ROM 3 (much harder-- a motherboard swap is required, and you might
as well purchase a ROM 3 system outright) it in order to run current
system software.

There is no such thing as a ROM 02 or 2. The engineers at Apple called
the first revision of the GS's ROM a ROM 00, and the second 01.
However, many people were confused by the second revision having a 1 in
the name. To get things back in sync, the third revision also has the
numeral 3 in the name. The ROM 4 existed in several prototypes, but was
killed off before general production.

The current system software works to make a ROM 01 and a ROM 3 two
systems appear almost identical to the software, except for the obvious
such as the amount of RAM built in. Certain games and other copy
protected software that used undocumented entry points on the ROM 01
will not work on the ROM 3.

More Infos at
http://myoldmac.net/cgi-data/forum/phpBB2/viewtopic.php?t=33

Best regards,

Oliver