> Interesting indeed, trashing the microcode would be somewhat lame, adding a
> "give kernel mode now" instruction - that would be art :-)
>
> side note: I'm told one of the early micros (6800????) had a "stop and catch
> fire" instruction. An invalid opcode that locked the cpu with all the
> internal bus drivers on causing the chip to burn itself out!
I'm sure the Intel People would understand the problems that would happen
if people discovered that microcode could be rewritten under "ordinary"
conditions.
You're probably thinking of a joke instruction called "Halt And Catch
Fire" which started sometime in the 60s or 70s. A not-too-reliable source
which I don't remeber says that one computer actually DID halt and catch
fire when someone executed HACF. The Commodore 1542 disk drive could be
burned out by having its 6502 processor execute some bad instructions. It
wasn't the processor's fault, but the implementation in the rest of the
drive. I think it was called the "Singing Disk Drive". It has been a
long time since I played with Commodore stuff, so I apologize for any
likely inaccuracies.
-- David Griffith dgriffi@ultrix6.cs.csubak.edu