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• hurricanezhb January 29, 2010 1:08 PM PST    about the reserved field in cpuid When using the cpuid, if the eax is set to some value such as 1, 3, 4, etc, the results (eax,ebx,ecx, edx) have some reserved field, for example, when eax==3, and run the cpuid, the result of eax and ebx are reserved. But if I run the cpuid with eax==3 or some others, what are the results of the reserved field? Is it time-changing or a undefined constant number that is consistant on every run for a cpu? jimdempseyatthecove February 2, 2010 9:35 AM PST Rate   #1 about the reserved field in cpuid I cannot answer for Intel but I can see some instances where the return value might not be constant. Examples might be CPUID return values may be dependent on BIOS settings If CPUID is extended to return core temperatures If CPUID is extended to return core frequencies If/When CPUID is used on system with hot plug/unplug processors. If/When CPUID is used on system with hot plug/unplug memory. etc... Note, I am not claiming nor suggesting that CPUID is used for any of these purposes. I am simply stating - do not assume values are fixed. Jim Dempsey Blog: The Parallel Void www.quickthreadprogramming.com Max Locktyukhin (Intel) February 5, 2010 12:51 PM PST Rate   #2 about the reserved field in cpuid Hello, yes, please, do not assume anything regarding to or rely on values of the reserved bits, they may and _do_ change from one processor to another. -Max

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