Red Hat Bugzilla – Bug 198349
Throttling states for Pentium 4 not fully operational
Last modified: 2015-01-04 17:27:53 EST
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)
Steps to Reproduce:
1. Install FC5 on a Pentium 4 system
2. Make the module "p4-clockmod" work
Only two out of eight throttling states work
the module should provide more throttling states
Everything else of power-saving features works correct (suspend, standby)
"cat /proc/acpi/processor/CPU1/throttling" says
state count: 8
active state: T0
so that more states possible.
Some steppings of the P4 have an errata which makes it risky to use the lower
states. Later kernels respect this.