On the 30th anniversary of the IIgs a new version of PRODOS has been released that runs on all Apple2 machines.
Prior releases of PRODOS blocked out the earlier machines by using 65c02 opcodes. PRODOS 2.4 supports all Apple2s all the way bay to the original 1977 Apple][ Integer ROM, all the way through to the ROM3 IIgs.
. . . .and the 2.4 release is not only smaller than the last official 2.0.3 release, it loads faster!
Also read about this release on Jason Scott’s blog
Apple ][ Forever!!!
PS, there is even a 2.4.1 release that can also run on Apple2 clones