From: email@example.com (Andre Fachat) > I am in the process of exending the VICE xpet emulator to emulate differe= > nt > PET models. So far 3xxx-8032 are working. The 2001 ROM seems to break > the IEEE488 emulation, but I didn't have time to look at it at all so far. > (I thought about a different EOI line, but first investigation didn't sup= > port > it so I need some more time) > If possible, I would like to have a copy of those ROMs too, to check them > on the emulator. The 2001 ROMs have a known bug in this department. When scrolling the screen, it blanks it by setting some output pin (to avoid snow?). The same pin is connected to the IEEE EOI line. Perhaps this is what you're running into. Later models (the 30xx ones) didn't have the screen blanking feature, but the ROMs still used it as if it did exist. If I recall right it was only properly fixed in the 4.0 ROMs. And then there was the "fast print poke". The printing routines only put characters in the screen during the vertical retrace. An input bit somehere indicated this condition. This poke turned the line into an output, so that printing would go much faster. On older machines it produced snow, too. On some machines it didn't work, caused weird screen output, or just plain destroyed them. I have seen the first two things but never the last. > Andre -Olaf. -- ___ Olaf 'Rhialto' Seibert rhialto(at)mbfys-dot-kun.nl "I would be dead in \X/ a week if I didn't do /something/. I'd be splattered all over the walls."
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