The phrase "Halt and Catch Fire" originated as engineering humor but became a technical reference for machine code that renders CPUs useless. IBM System/360 processors could literally catch fire when encountering certain invalid opcodes, while Motorola 6800 had undocumented instructions that locked up the processor.

In 1977, Gerry Wheeler documented two specific opcodes ($9D and $DD) in BYTE magazine that caused the program counter to advance through memory like a hardware counter. The processor would continuously read memory without processing any data, requiring a reset to recover. Wheeler nicknamed these instructions Halt and Catch Fire, acknowledging the dramatic name was his own creation.

These hardware vulnerabilities persist across processor generations, from the Pentium F00F bug to modern x86 processors that still reveal unexpected states under fuzzing. The behavior serves as a reminder that beneath sophisticated software stacks, processors remain physical devices with tangible failure modes that testing methods continue to uncover.