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| author | Dave Jones <davej@delerium.codemonkey.org.uk> | 2004-06-14 00:12:36 +0100 |
|---|---|---|
| committer | Dave Jones <davej@delerium.codemonkey.org.uk> | 2004-06-14 00:12:36 +0100 |
| commit | b982274d97de87688c1da6deef480fa2cef20c1c (patch) | |
| tree | 2208843a283e01f55633e26f41a3d2701600f7f6 /Documentation | |
| parent | ea59d34d21dd793a2500c61834c17fe89afe12bf (diff) | |
| parent | 1a9325fb3f679b86005095f49ce1e4956209820e (diff) | |
| download | history-b982274d97de87688c1da6deef480fa2cef20c1c.tar.gz | |
Merge delerium.codemonkey.org.uk:/mnt/data/src/bk/bk-linus
into delerium.codemonkey.org.uk:/mnt/data/src/bk/cpufreq
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/cpu-freq/amd-powernow.txt | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/Documentation/cpu-freq/amd-powernow.txt b/Documentation/cpu-freq/amd-powernow.txt new file mode 100644 index 0000000000000..254da155fa47d --- /dev/null +++ b/Documentation/cpu-freq/amd-powernow.txt @@ -0,0 +1,38 @@ + +PowerNow! and Cool'n'Quiet are AMD names for frequency +management capabilities in AMD processors. As the hardware +implementation changes in new generations of the processors, +there is a different cpu-freq driver for each generation. + +Note that the driver's will not load on the "wrong" hardware, +so it is safe to try each driver in turn when in doubt as to +which is the correct driver. + +Note that the functionality to change frequency (and voltage) +is not available in all processors. The drivers will refuse +to load on processors without this capability. The capability +is detected with the cpuid instruction. + +The drivers use BIOS supplied tables to obtain frequency and +voltage information appropriate for a particular platform. +Frequency transitions will be unavailable if the BIOS does +not supply these tables. + +6th Generation: powernow-k6 + +7th Generation: powernow-k7: Athlon, Duron, Geode. + +8th Generation: powernow-k8: Athlon, Athlon 64, Opteron, Sempron. +Documentation on this functionality in 8th generation processors +is available in the "BIOS and Kernel Developer's Guide", publication +26094, in chapter 9, available for download from www.amd.com. + +BIOS supplied data, for powernow-k7 and for powernow-k8, may be +from either the PSB table or from ACPI objects. The ACPI support +is only available if the kernel config sets CONFIG_ACPI_PROCESSOR. +The powernow-k8 driver will attempt to use ACPI if so configured, +and fall back to PST if that fails. +The powernow-k7 driver will try to use the PSB support first, and +fall back to ACPI if the PSB support fails. A module parameter, +acpi_force, is provided to force ACPI support to be used instead +of PSB support. |