Processor upgrade in PowerMac 8500/120 broke MkLinux at the
splash screen with an "unimplemented trap" bomb.
As part of the processor upgrade it was necessary to press a reset
button on the motherboard to allow the Mac to recognise the new
processor card. I assume that this button did something to scramble
the PRAM thus forcing the Mac to examine the processor card to get
the details. The scrambled PRAM interfered with the boot process for
MkLinux. Regardless of what configuration I tried after that, even
the original hardware configuration, nothing would boot. Once I reset
the date and time from the Mac Control Panel the problem in the PRAM
was restored and MkLinux happily booted again (2.5 days of trying
many different things later). I am assuming that this is the cause
of the problem and my reasoning is correct.
Alan Chapman email@example.com@usq.edu.au