Processor Update Feature
All processors can contain design defects or errors. Many times, the effects of any given bug can be avoided by implementing hardware or software workarounds. Intel documents these bugs and workarounds well for its processors in its processor Specification Update manual; this manual is available from Intel's Web site. Most of the other processor manufacturers also have bulletins or tips on their Web sites listing any problems or special fixes or patches for their chips.
Previously, the only way to fix a processor bug was to work around it or replace the chip with one that had the bug fixed. Now, a new feature built into the Intel P6 and P7 processors, including the Pentium Pro through Pentium III, Celeron, and Pentium 4, can allow many bugs to be fixed by altering the microcode in the processor. Microcode is essentially a set of instructions and tables in the processor that control how the processor operates. These processors incorporate a new feature called reprogrammable microcode, which enables certain types of bugs to be worked around via microcode updates. The micro code updates reside in the motherboard ROM BIOS and are loaded into the processor by the motherboard BIOS during the POST. Each time the system is rebooted, the fix code is reloaded, ensuring that it will have the bug fix installed anytime the processor is operating.
The updated microcode for a given processor is provided by Intel to the motherboard manufacturer so it can incorporate the microcode into the flash ROM BIOS for the board. This is one reason it is important to install the most recent motherboard BIOS anytime you install a new processor. If your processor is newer than your motherboard ROM BIOS code, it probably doesn't include updated microcode to support your processor. In that case, you should visit the Web site of your motherboard manufacturer so you can download and install the latest BIOS update for your motherboard.
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