I am having a problem booting into ProDOS with my latest hardware emulator. When I boot from a ROM drive without the floppy ROM, ProDOS boots correctly. But when the ROM for the floppy is visable, ProDOS seems to go into neverland. Depending on the contents of memory, it can do almost anything. I traced the boot process and it appears that when the ROM is visable, some code is missed and when a RTS is executed, there is some extra data still on the stack and this becomes the program counter. And this is why the RAM contents affect what happens.
But when I remove the ROM, ProDOS boots correctly and there seems to not be any other issues. I was able to run the Basic Interpreter, Copy II+, Filer, and the Copy II+ Nibble copier. Even thought since I had not floppies the nibble copier did not like the machine configuration. Apparently ProDOS is not going to the floppy card registers, but it does something different depending if the ROM is present or not.
I am booting ProDOS 8 Version 1.9 since this was the last version that would run on a NMOS 6502.
Anyone have any ideas? Or is this technology too old and no one knows any more?