Red Hat Bugzilla – Bug 171533
Frequency in /proc/cpuinfo and /sys/.../cpuinfo_cur_freq differ
Last modified: 2007-11-30 17:07:21 EST
From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20050921 Red Hat/1.0.7-1.4.1 Firefox/1.0.7 Description of problem: I've got a Pentium D 830 in a Dell Dimension 9100. According to Intels hardware specification Speed Step is available for this processor. cpuspeed is running and is telling me it can switch frequencies between 2.8 GHz and 3.0 GHz. When I query /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq it is telling me most of the time the CPU(s) are running at 2.8 GHz. Exactly what I expect. However /proc/cpuinfo always shows the CPUs running at 3.0 GHz. If I take a look at my Notebook, the frequencies in /proc/cpuinfo and /sys/devices/.../cpuinfo_cur_freq change in sync. Even when I send a SIGUSR2 to cpuspeed the frequency in /proc/cpuinfo does not change. Version-Release number of selected component (if applicable): kernel-smp-2.6.9-22.EL How reproducible: Always Steps to Reproduce: 1. cat /proc/cpuinfo 2. cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq Actual Results: Frequencies differ. Expected Results: Frequencies are identical Additional info:
Created attachment 120281 [details] Output of /proc/cpuinfo
The P4D can't do speedstep, but the frequency can be changed by the BIOS. The frequency in /sys is the current frequency of the CPU, and the one is /proc/cpuinfo is the canonical frequency. Therefore, the behavior that you are seeing is expected and gives no cause for alarm.