Pentium F00F bug

The Pentium F00F bug, shorthand for F0 0F C7 C8, the hexadecimal encoding of one offending instruction, more formally, the invalid operand with locked CMPXCHG8B instruction bug, is a design flaw in the majority of Intel Pentium, Pentium MMX, and Pentium OverDrive processors (all in the P5 microarchitecture).

Pentium F00F bug

The Pentium F00F bug, shorthand for F0 0F C7 C8, the hexadecimal encoding of one offending instruction, more formally, the invalid operand with locked CMPXCHG8B instruction bug, is a design flaw in the majority of Intel Pentium, Pentium MMX, and Pentium OverDrive processors (all in the P5 microarchitecture).