Issue:

Systems using the Intel i3-5010U, Intel I5-5300U and I7-5600U processors will scale down to only 800MHz when cpu frequency scale down commands are issued. This is the actual physical hardware limit for these processors and is not an error.

Environment:

RHEL6
RHEL7
Intel i3-5010U Processor
Intel i5-5200U Processor
Intel i5-5300U Processor
Intel i7-5600U Processor
CPU scaling - power states

Diagnostic:

This is not an issue with the driver or the Operating System. Both intel_pstate and acpi_cpufreq are correctly running at ~800Mhz when the minimum frequency is called for. However, both the ACPI PSS table (used by acpi_cpufreq) and the MSR_PLATFORM_INFO MSR incorrectly report 500Mhz as the minimum hardware limit for this processor.

Resolution:

Red Hat and Intel are aware of this issue, and are collaborating on a fix. The minimum hardware limits of the processors are 800MHz, and affected systems will correctly scale down to this speed during power scale down operations. Any error messages reported during power scale down operations may be safely ignored. A fix will be released for this bug in a future update.

Please contact your Red Hat support representative for further details if desired.