properly again! I believe this is the first time
I've run into a
faulty
CPU in a vintage computer (or peripheral).
Wow, that's bizarre. 6502s don't fail very often.
I can't remember if I'ev ever had to replace a 6502, but I've
certainly
had other CPUs fail. Z80, 8085, 6800, 8035 (fortunately ROMless),
some
6803-seires microcontrolelr (again ROMless), and so on.
My expeirence, as I've said beore is that while LSI ICs (including
microprocessors) are more reliable than the same circuit built from
TTL or
discretes, the LSI chips are less reliable than idividualt TTL ICs.
-tony
I once had an 8088 that behaved very strangely, it read the correct
opcodes from memory but executed something completely different
sometines. It turned out that the voltage between the +5V pin and the 0V
pin was something like 4.65V. 0.1V too low a voltage was enough to make
it execute some code correctly and other code completely wrong. Since
then I always check the voltage at the chip's pins if strange things are
happening.
/Jonas
