🚀 go-pugleaf

pet...@opus.cs.mcgill.ca (Peter Deutsch) writes:

>In article <1713@cygnus.scol.UUCP>, davidgu@scol.UUCP (David Gurr) writes:
>> dc...@cssun.tamu.edu (David A. Cook) writes:
>> 
>> >In article <ben.2630@epmooch.UUCP> ben@epmooch.UUCP (Rev. Ben A. Mesander) 
>> >writes:
>> >> If memory serves me right, the old Commodore PET machines could be
>> >> physically damaged (ie smoke) by poking the wrong value into the wrong
>> >> memory location. Good design...
>> 
>> Didn't there use to be a machine intrsuction that caused this problem?
>> Some wag gave it the mnemonic HCF ... Halt and Catch Fire!

No. The PET used the Mos Technology 6502 processor. HCF is a 6800
instruction.

The Motorola 6800 processor had an undocumented instruction
(code 0x9d), which transformed the cpu into a fast binary counter
on the address bus. It was otherwise dead, not even a NMI could
awake it. I got this information (and the mnemonic HCF, Halt and
Catch Fire for the instruction) from an article in Byte:

   G. Wheeler, "Undocumented M6800 instructions", Byte, 
   December 1977, page 46-48

The purpose of this instruction was perhaps some kind of 
factory test. I don't think it could do any hardware damage.

Wolfgang Strobl
#include <std.disclaimer.hpp>