On Tue, May 27, 2014 at 2:08 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
   Halt and Catch
Fire is not a real computer instruction that caused a race
 condition that made the computer stop working.  I imagine a bunch of
 teenagers are scouring Intel technical manuals looking for the Code 2 Duo
 equivalent of HCF. 
 I thought there was at least one microprocessor (Motorola 6800?) where an
 undocumented instruction would cause the processor to simply do memory
 cycles at the fasted posible rate, address incrementing each time, and
 the procesosr ignored all inputs apart from reset.
 While the machine did not catch fire, the system was essentailly locked
 up until the hardware reset.
 -tony