AMD AMD-K6-2/450 Design Guide - Page 69
Embedded AMD Processor Recognition, CPUID Instruction Overview - speed
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23913A/0-November 2000 Preliminary Information Embedded AMD-K6™ Processors BIOS Design Guide Embedded AMD Processor Recognition The CPUID instruction provides a simple way for hardware and software to identify the type of processor and its feature set. After detecting the processor and its capabilities, software can be accurately tuned to the system for optimal performance and benefit to users. s For example, game software can test the performance level available from a particular processor by detecting the type or speed of the processor. If the features warrant executing additional capabilities or advanced algorithms, these can be enabled with software. s Another example involves testing for the presence of 3DNow! or MMX instructions on the processor. If the software finds these features present when it checks the feature bits, it can utilize these more powerful extensions for dramatically better performance on new multimedia software. See http://www.amd.com/products/cpg/bin for example software and source code to detect processor information. CPUID Instruction Overview Software operating at any privilege level can execute the CPUID instruction to identify the processor and its feature set. In addition, the CPUID instruction implements multiple functions, each providing different information about the processor, including the vendor, model number, revision (stepping), features, cache organization, and processor name. The multiple-function approach allows the CPUID instruction to return a complete picture about the type of processor and its capabilities - more detailed information than could be returned by a single function. The CPUID instruction provides the flexibility of making only one call to obtain the specific data requested. The functions are divided into two types: standard functions and extended functions. Embedded AMD Processor Recognition 57