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Bug #13962

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Support using CPUID instruction for TSC frequency when available

Added by Jason King 3 months ago.

Status:
New
Priority:
Normal
Assignee:
Category:
kernel
Start date:
Due date:
% Done:

0%

Estimated time:
Difficulty:
Medium
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Gerrit CR:

Description

Intel has introduced CPUID leaf 0x15 which returns the following (on supported platforms):

EAX = numerator of TSC frequency / core crystal clock frequency
EBX = denominator of TSC frequency / core crystal clock frequency (if != 0)
ECX = core crystal clock frequency (in Hz, as an unsigned int)

When the CPUID instruction indicates support for this leaf, and the resulting values are non-zero, this can be used to determine the TSC frequency.

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