diff options
author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
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 000000000000..254da155fa47 --- /dev/null +++ b/Documentation/cpu-freq/amd-powernow.txt | |||
@@ -0,0 +1,38 @@ | |||
1 | |||
2 | PowerNow! and Cool'n'Quiet are AMD names for frequency | ||
3 | management capabilities in AMD processors. As the hardware | ||
4 | implementation changes in new generations of the processors, | ||
5 | there is a different cpu-freq driver for each generation. | ||
6 | |||
7 | Note that the driver's will not load on the "wrong" hardware, | ||
8 | so it is safe to try each driver in turn when in doubt as to | ||
9 | which is the correct driver. | ||
10 | |||
11 | Note that the functionality to change frequency (and voltage) | ||
12 | is not available in all processors. The drivers will refuse | ||
13 | to load on processors without this capability. The capability | ||
14 | is detected with the cpuid instruction. | ||
15 | |||
16 | The drivers use BIOS supplied tables to obtain frequency and | ||
17 | voltage information appropriate for a particular platform. | ||
18 | Frequency transitions will be unavailable if the BIOS does | ||
19 | not supply these tables. | ||
20 | |||
21 | 6th Generation: powernow-k6 | ||
22 | |||
23 | 7th Generation: powernow-k7: Athlon, Duron, Geode. | ||
24 | |||
25 | 8th Generation: powernow-k8: Athlon, Athlon 64, Opteron, Sempron. | ||
26 | Documentation on this functionality in 8th generation processors | ||
27 | is available in the "BIOS and Kernel Developer's Guide", publication | ||
28 | 26094, in chapter 9, available for download from www.amd.com. | ||
29 | |||
30 | BIOS supplied data, for powernow-k7 and for powernow-k8, may be | ||
31 | from either the PSB table or from ACPI objects. The ACPI support | ||
32 | is only available if the kernel config sets CONFIG_ACPI_PROCESSOR. | ||
33 | The powernow-k8 driver will attempt to use ACPI if so configured, | ||
34 | and fall back to PST if that fails. | ||
35 | The powernow-k7 driver will try to use the PSB support first, and | ||
36 | fall back to ACPI if the PSB support fails. A module parameter, | ||
37 | acpi_force, is provided to force ACPI support to be used instead | ||
38 | of PSB support. | ||