Simon Williams writes ...
> 
> I've occasionally seen reference to the ROM1 GS being "more compatible"
> than the ROM3... does this refer to 8-bit-compatibility or compatibility
> with older GS software?
> 
> I've occasionally seen reference to the ROM1 GS being "more compatible"
> than the ROM3... does this refer to 8-bit-compatibility or compatibility
> with older GS software?
 ....

     It refers to compatibility with older GS software.

     Here's some info on GS System versions which helps show which ROM models
are most likely to be compatible with software released under a particular
System:


System       GS/OS         Date        Tool Patches     Finder
6.0.1        v4.02       06-May-93     ROM-01, ROM 3      6.x
6.0.0        v4.01       04-Mar-92     ROM-01, ROM 3      6.0
5.0.4        v3.03       20-Aug-90     ROM-01, ROM 3      1.3
5.0.0        v3.00       14-Jun-89     ROM-01, ROM 3      1.3
4.0.0        v2.00       18-Aug-88     ROM-00, ROM-01     1.2

System    P16 & Loader     Date
3.2          v1.6        14-Jun-88     ROM-00, ROM-01     1.1
3.1          v1.3        29-Jun-87                        1.0
3.0          v1.3        29-Jun-87                        1.0
2.0          v1.2        18-May-87                       Desktop
1.1          v1.1         2-Dec-86                       Desktop


     Running a particular piece of software doesn't necessarily involve parts
of System which are changed (or changed enough to have much impact).  So,
newer GS's can run lots of the old stuff.



Rubywand



Mark Percival writes ...

 ....
> 
> I think System 4.0 dropped support for the ROM 00.
> 
 ....

     Think that must be so. The Sound Ace diskette (Sys 4) which supposedly
has the ROM-00 patch file doesn't. Neither does the Sys 4 set on the Golden
Orchard CD.


> I have never heard of System 3.0, just 3.1.

     A System 3.0 was mentioned as a possibility in a posting; but, I've
never come across a System 3.0 diskette, either.


> 
> >2.0          v1.2        18-May-87                       Desktop
> >1.1          v1.1         2-Dec-86                       Desktop
> 
> I don't think System 1.x was supported on the ROM 01.  I think it ran
> but you could have problems with it in this configuration.

     Yes; the problems show up in stuff like the original Apple IIgs Tour
diskette. Fortunately, a lot of the very early IIgs stuff is ProDOS-8 and
runs fine under System 6.0.1. And, some early ProDOS-16 classics, Like Tower
of Myraglen, strart up and run fine from the System 6.0.1 Finder.


     So, the current list looks like this ...

System       GS/OS         Date        Tool Patches     Finder
6.0.1        v4.02       06-May-93     ROM-01, ROM 3      6.x
6.0.0        v4.01       04-Mar-92     ROM-01, ROM 3      6.0
5.0.4        v3.03       20-Aug-90     ROM-01, ROM 3      1.3
5.0.0        v3.00       14-Jun-89     ROM-01, ROM 3      1.3
4.0.0        v2.00       18-Aug-88     ROM-01             1.2

System    P16 & Loader     Date
3.2          v1.6        14-Jun-88     ROM-00, ROM-01     1.1
3.1          v1.3        29-Jun-87                        1.0
2.0          v1.2        18-May-87                       Desktop
1.1          v1.1         2-Dec-86                       Desktop


     Think there was also a System 4.0.1 and a 5.0.3; but, no specific info
at present.



Rubywand