组装CPU频率测量算法 [英] Assembly CPU frequency measuring algorithm

问题描述

用于测量处理器频率的常用算法有哪些?

What are the common algorithms being used to measure the processor frequency?

推荐答案

Core Duo 之后的 Intel CPU 支持两个 Model-Specific 寄存器，称为 IA32_MPERF 和 IA32_APERF.
MPERF以CPU支持的最大频率计数，APERF以当前实际频率计数.

Intel CPUs after Core Duo support two Model-Specific registers called IA32_MPERF and IA32_APERF.
MPERF counts at the maximum frequency the CPU supports, while APERF counts at the actual current frequency.

实际频率由下式给出:

您可以通过此流程阅读它们

You can read them with this flow

; read MPERF
mov ecx, 0xe7
rdmsr
mov mperf_var_lo, eax
mov mperf_var_hi, edx

; read APERF
mov ecx, 0xe8
rdmsr
mov aperf_var_lo, eax
mov aperf_var_hi, edx

但注意rdmsr是特权指令，只能在ring 0中运行.

but note that rdmsr is a privileged instruction and can run only in ring 0.

我不知道操作系统是否提供了一个接口来读取这些，虽然它们的主要用途是用于电源管理，所以它可能没有提供这样的接口.

I don't know if the OS provides an interface to read these, though their main usage is for power management, so it might not provide such an interface.

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