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Embedded Systems

The Pentium F00F Bug

By Robert R. Collins, May 01, 1998

When x86 processors encounter an invalid instruction, the processor is supposed to generate an invalid opcode exception. If this mechanism fails, however, the program can bring the system down -- and that's what happens with the F00F bug.


The Pentium F00F Bug

The Pentium F00F Bug

By Robert R. Collins

Dr. Dobb's Journal May 1998 

Sequence  Address   Data      Mnemonic                        Timestamp
-------------------------------------------------------------------------
  428677  00060FF8  0008049A    ( LOCKED MEM READ )              330 ns
          00060FFC  00008E00    ( LOCKED MEM READ )
  428678  0001E8B8  BFF0FFFF    ( LOCKED MEM READ )              170 ns
          0001E8BC  00009B01    ( LOCKED MEM READ )
  428679  0001EE9C  00000008    ( LOCKED MEM WRITE )            130 ns
  428680  0001EE98  000003F2    ( MEM WRITE )                    60 ns

Example 2: F00F bug on noncacheable page.

Copyright © 1998, Dr. Dobb's Journal



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