Paul W. Good wrote: > What differences are there in the IIGS ROM0 and ROM1 machines? > > 1. In the ROMs themselves? Lots of little odds and ends. The main difference is that ROM 01 has newer versions of the low-level toolsets (version 2.0 of toolsets 1 through 13, instead of version 1.0), incorporating a lot of bug fixes. The majority of these are also fixed on a ROM 00 machine by running new enough system software (System 2.0 or later), because the system software loads the patches into RAM at startup time. If you are running old system software, the main benefit of ROM 01 is that it will free up some RAM that would otherwise be occupied by these patches, and the same bugs are fixed if you run System 1.0 or 1.1 on a ROM 01. There is a technical note (TN.IIGS.026) which summarises the changes in ROM 01 (which it confusingly calls "ROM 2.0"). Apart from toolbox changes, the other significant ones I can spot from a quick glance include: - Detection of disk changes in the Apple 3.5 Drive works correctly. - AppleTalk bug fixes. - Applesoft handles horizontal tabbing correctly in 80-column mode. - Maximum RAM disk size increased to almost 8 MB (instead of 4 MB). - Interrupt handler bug fixes. - New monitor command (#) to enable some debugging desk accessories. - New monitor command (Ctrl-N) to set native mode. - Serial firmware bug fixes and improvements. - SmartPort (slot 5) firmware has some bug fixes and better performance. The most significant difference between ROM 00 and 01 is the fact that System 4.0 and later (all system software based on GS/OS) will not run on ROM 00 - it requires ROM 01 (or ROM 3, which has a different motherboard). You may run into some old software which only works on ROM 00, because the software broke the rules about how to use the firmware, or relied on old bugs which were fixed. > 2. In the motherboards? No difference at all. All that changed was the ROM chip itself. There is one point worth mentioning here: early IIgs machines also had a faulty Video Graphics Controller chip, which could also be upgraded for free at the same time as the ROM 01 upgrade. The symptom of the VGC fault was that monochrome double hi-res graphics mode produced pink fringing effects (it should have been pure black and white) and/or flickering pixels. Some machines (including mine) exhibited the same symptoms in 80-column text mode, with variable effects depending on the foreground and background colours. > The location of a file on the Internet describing the differences > would be great. If you can find an archive of the Apple II technical notes out there, have a look for TN.IIGS.026 (in the IIGS folder). (I have no idea whether anyone has them online - I have the full set on my Mac's hard drive, and I only ever accessed them on Apple's FTP site, but they removed them several years ago.) If you got your version numbers muddled up and were actually wondering about the differences between ROM 01 and ROM 3, then that is a different kettle of fish. There have been discussions posted here on the subject in the past, and I could dig through my archives to find one of my earlier postings.