On Wed, 28 Dec 2005, TomCh wrote:
Ultima III sets up the addr of the IRQ handler in $3FE/F, but AppleWin's Apple][+ ROM has $FFFE/F = $FF59 = OLDRST. If I modify this via AppleWin's monitor (me fffe 40 fa), then Ultima III's MB playback routine works (the mod patches the ROM to vector to $FA40 = OLDIRQ). I don't understand why the ROM would vector to OLDRST on an IRQ (I can't believe that it's been patched to do this!). The ID bytes indicate that it's an Apple][+ ROM.
I have a few variant Apple ][+ ROM dumps and assemblies lying around. They have IRQ properly vectored to $FA40 "newirq". You could always replace the monitor code with mine. xD; or replace the rom with FPBASIC from the 1980 system disk.
-uso.