The problem:
 
Processor upgrade in PowerMac 8500/120 broke MkLinux at the 
splash screen with an "unimplemented trap" bomb.
 
The solution:
 
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  chapman@usq.edu.au