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[ The PC Guide | Systems and Components Reference Guide | The Processor | Processor Architecture and Operation | Internal Processor Interfaces and Operation | Processor Instruction Sets ]

Pentium and Pentium Pro Instruction Set Extensions

Intel's latest processors added a few instructions to the standard x86 instruction set used in 386 and 486 chips. Some programs (notably games) can be optimized to deliver higher performance on these processors by making use of these specific instructions. Very little software has actually been written to use these instructions. Some games however do use them, which is one reason why some of them will detect the processor in the PC and refuse to run if they do not find a Pentium.

Warning: It is very important to realize that some of the Pentium "compatible" processors are only mostly Pentium-compatible. For example, Cyrix's 6x86 processor is a Pentium-class CPU, but was designed independently of the Pentium to support the generic x86 instruction set. It does not implement the Pentium-specific instructions and will not run software that requires them. This is not a concern for the majority of mainstream software but is a concern for some programs. As Cyrix and AMD processors become more popular I expect that there will be more and more incentive for programmers to avoid the use of processor-specific instructions.

Next: MMX Instructions


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