linux/Documentation/cpu-freq/amd-powernow.txt
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   1
   2PowerNow! and Cool'n'Quiet are AMD names for frequency
   3management capabilities in AMD processors. As the hardware
   4implementation changes in new generations of the processors,
   5there is a different cpu-freq driver for each generation.
   6
   7Note that the driver's will not load on the "wrong" hardware,
   8so it is safe to try each driver in turn when in doubt as to
   9which is the correct driver.
  10
  11Note that the functionality to change frequency (and voltage)
  12is not available in all processors. The drivers will refuse
  13to load on processors without this capability. The capability
  14is detected with the cpuid instruction.
  15
  16The drivers use BIOS supplied tables to obtain frequency and
  17voltage information appropriate for a particular platform.
  18Frequency transitions will be unavailable if the BIOS does
  19not supply these tables.
  20
  216th Generation: powernow-k6
  22
  237th Generation: powernow-k7: Athlon, Duron, Geode.
  24
  258th Generation: powernow-k8: Athlon, Athlon 64, Opteron, Sempron.
  26Documentation on this functionality in 8th generation processors
  27is available in the "BIOS and Kernel Developer's Guide", publication
  2826094, in chapter 9, available for download from www.amd.com. 
  29
  30BIOS supplied data, for powernow-k7 and for powernow-k8, may be
  31from either the PSB table or from ACPI objects. The ACPI support
  32is only available if the kernel config sets CONFIG_ACPI_PROCESSOR.
  33The powernow-k8 driver will attempt to use ACPI if so configured,
  34and fall back to PST if that fails.
  35The powernow-k7 driver will try to use the PSB support first, and
  36fall back to ACPI if the PSB support fails. A module parameter,
  37acpi_force, is provided to force ACPI support to be used instead 
  38of PSB support.
  39
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