Bug 198349 - Throttling states for Pentium 4 not fully operational
Throttling states for Pentium 4 not fully operational
Product: Fedora
Classification: Fedora
Component: kernel (Show other bugs)
i686 Linux
medium Severity medium
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Assigned To: Dave Jones
Brian Brock
Depends On:
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Reported: 2006-07-11 06:06 EDT by Ronny Fischer
Modified: 2015-01-04 17:27 EST (History)
2 users (show)

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Doc Type: Bug Fix
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Last Closed: 2006-07-25 23:00:49 EDT
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Description Ronny Fischer 2006-07-11 06:06:55 EDT
Description of problem:

The module "p4-clockmode" provides only two different throttling speed states 
(100% and 87%) so that the Pentium 4 is nearly always at high speed. The same 
module at FC4 provided all eight different throttling states.

Version-Release number of selected component (if applicable):

Fedora Core 5, Kernel 2.6.17-1-2145_FC5, Intel 875PZLK Mainboard with latest 
BIOS, Pentium 4 2.6 GHz, HT disabled (with HT enabled it's the same)

How reproducible:


Steps to Reproduce:
1. Install FC5 on a Pentium 4 system
2. Make the module "p4-clockmod" work
Actual results:

Only two out of eight throttling states work

Expected results:

the module should provide more throttling states

Additional info:

Everything else of power-saving features works correct (suspend, standby)

"cat /proc/acpi/processor/CPU1/throttling" says

state count:             8
active state:            T0
   *T0:                  00%
    T1:                  12%
    T2:                  25%
    T3:                  37%
    T4:                  50%
    T5:                  62%
    T6:                  75%
    T7:                  87%

so that more states possible.
Comment 1 Dave Jones 2006-07-25 23:00:49 EDT
Some steppings of the P4 have an errata which makes it risky to use the lower
states. Later kernels respect this.

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