diff options
author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/cpu-freq/amd-powernow.txt |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'Documentation/cpu-freq/amd-powernow.txt')
-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 00000000000..254da155fa4 --- /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. |