acpi-cpufreq dissapires when FSB is changed

kernel 2.6.23
intel p35 board
core2duo e6750 (6x333=2000MHz, 8x333=2667MHz)

when it runs on default FSB (333MHz) it looks like this:
uname -a
Linux tnt 2.6.23-gentoo #3 SMP Sun Oct 21 15:37:59 CEST 2007 x86_64 Intel(R) Core(TM)2 Duo CPU E6750 @ 2.66GHz GenuineIntel GNU/Linux ls -lah /sys/devices/system/cpu/cpu0/cpufreq/
total 0
drwxr-xr-x 4 root root 0 Oct 18 17:19 .
drwxr-xr-x 6 root root 0 Oct 18 17:19 ..
-r--r--r-- 1 root root 4.0K Oct 18 17:24 affected_cpus -r--r--r-- 1 root root 4.0K Oct 18 17:24 cpuinfo_max_freq -r--r--r-- 1 root root 4.0K Oct 18 17:24 cpuinfo_min_freq
drwxr-xr-x 2 root root 0 Oct 18 17:24 ondemand
-r--r--r-- 1 root root 4.0K Oct 18 17:24 scaling_available_frequencies -r--r--r-- 1 root root 4.0K Oct 18 17:24 scaling_available_governors -r--r--r-- 1 root root 4.0K Oct 18 17:24 scaling_cur_freq -r--r--r-- 1 root root 4.0K Oct 18 17:24 scaling_driver
-rw-r--r-- 1 root root 0 Oct 18 17:19 scaling_governor
-rw-r--r-- 1 root root 4.0K Oct 18 17:24 scaling_max_freq -rw-r--r-- 1 root root 4.0K Oct 18 17:24 scaling_min_freq
drwxr-xr-x 2 root root 0 Oct 18 17:24 stats
cat /proc/cpuinfo |grep MHz
cpu MHz : 2000.000
cpu MHz : 2000.000

when FSB is changed (400MHz) it looks like this:
uname -a
Linux tnt 2.6.23-gentoo #3 SMP Sun Oct 21 15:37:59 CEST 2007 x86_64 Intel(R) Core(TM)2 Duo CPU E6750 @ 2.66GHz GenuineIntel GNU/Linux ls -lah /sys/devices/system/cpu/cpu0/cpufreq/
ls: cannot access /sys/devices/system/cpu/cpu0/cpufreq/: No such file or directory
cat /proc/cpuinfo |grep MHz
cpu MHz : 3200.000
cpu MHz : 3200.000

the only thing that was changed in BIOS is FSB freq. no power-saving options were changed.

so, in other operating systems frequency scaling continue to work using the same multiplier-voltage data (for e6750 it's 1.15V for 6x and 1.35V for 8x). it leads to 2.4GHz @1.15V and 3.2GHz @1.35V and that is far from unstable for this CPU (the one I own is rock stable at 2.4GHz @1.01V and 3.2GHz @1.26V).

before this Intel CPU, I had experiance with Athlon64 CPUs and powernow-k8 cpufreq driver. it has been using multiplier-voltage data no matter what FSB freq was specified, just like windows does with core2duo CPUs. that was much more flexibile and usefull.

here, I guess, acpi-cpufreq can not locate data for 2.4GHz and 3.2GHz freqs and fails to work.

is there any way to make acpi-cpufreq use multiplier-voltage instead of frequency-voltage pairs?

No. It's using tables that come from the BIOS. When you overclock, those tables are no longer correct, so it can't work.

Dave

http://www.codemonkey.org.uk