Powernow-K7.

BIOS problems.

Several laptops have serious problems with the PST tables in their BIOS.
This meant that until version 2.6.6 of the kernel, Powernow was non functional on these laptops.
Typical problems include:

  • No cpuid table matching the cpuid of the CPU.
  • No entries in the cpuid table matching the CPU.
  • Multiple definitions of the same values (no alternatives) in the PST table.
  • Too few choices in the PST table. (In this case, the driver is usable, but very limited).

If you're wondering "But windows works", it's because it likely uses ACPI for its CPU scaling instead of a native driver.
As of 2.6.6rc3, the powernow-k7 driver will fall back to using ACPI tables if the PST looks to be broken.
Reports seem to suggest that this fixes these problems.

Laptops known to have some problem or other:

Laptop Problem/Notes
Acer Aspire 1352XC Has 8 PST tables. None of which match the cpuid of the processor (0x781)
Compaq Evo N115. Has 21 PST tables. None of which match the cpuid of the processor (0x771)
Compaq MX9005. Has 14 PST tables. None of which match the cpuid of the processor
Compaq NX9005. Has 14 PST tables. None of which match the cpuid of the processor (0x7A0)
Compaq Presario 2100. Has 14 PST tables. None of which match the cpuid of the processor (0x7A0)
eMachines M5305. Has 43 PST tables, None of which match the cpuid of the processor (0x7A0)
eMachines M5310.
Fujitsu Siemens Amilo A7600. Has 14 PST tables. None of which match the cpuid of the processor (0x781)
Hewlett Packard Pavillion ZE4521EA. Has 14 PST tables. None of which match the cpuid of the processor (0x7A0)
Hewlett Packard Pavillion ZE4357EA. Has 14 PST tables. None of which match the cpuid of the processor (0x7A0)
Hewlett Packard Pavillion ZE4360EA. Has ?? PST tables. None of which match the cpuid of the processor (0x7A0)
Hewlett Packard Pavillion ZE4417EA.
Sony VAIO PCG-FX502.

*NB* Please note that if you are trying to get a mobile Athlon/Duron to work in a desktop board, and are puzzled as to why the driver is failing, it is because the driver needs certain tables to be present in the BIOS. Desktop boards typically don't have powernow tables. There are some patches in the cpufreq archives to hardcode values into the driver. At this time, these aren't considered for inclusion. For more info, See this page.

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