FSB Underclocking

[vent83]

Is there a way to set the FSB frequency? And if there are several ways - which is the most official/supported way? Can it be done for example in some conjunction with CPU frequency scaling (like Speedstep) and undervolting?

I have an Acer TravelMate 4101WLMi laptop and under Windows i have a brilliant manufacturer-made tool for power management, which allows me to set the following configuration:

Speed [MHz] Bus [MHz] Rated Bus [MHz] Voltage [VID]
-----------------------------------------------------------------------
600 100 400 0.988
800 133 533 0.988
1600 133 533 1.308

Especially the lowest configuration is very desireable, because it causes the fan not to turn on *at all*, and I haven't been able to achieve it with the standard kernel - the Speedstep only allows me to set the middle configuration as the lowest (it does not change the FSB frequency).

Thanks in advance for any advice.



Processor:
Intel Pentium M 730 (Dothan), Socket 479 mPGA

processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 13
model name : Intel(R) Pentium(R) M processor 1.60GHz
stepping : 8
cpu MHz : 800.000
cache size : 2048 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat clflush dts acpi mmx fxsr sse sse2 ss tm pbe nx up est tm2
bogomips : 1597.74
clflush size : 64

[alex.blackbit]

i do not know actually, but maybe one of these helps

Code: Select all

ahuemer@xeon ~ % eix -cC sys-power cpu
[N] sys-power/cpuspeedy (0.4.1): A simple and easy to use program to control the speed and the voltage of CPUs on the fly.
[N] sys-power/gtk-cpuspeedy (0.3.0-r1): Graphical GTK+-2 frontend for cpuspeedy
[N] sys-power/ncpufreqd ((~)2.4): Daemon controlling CPU speed and temperature
[N] sys-power/cpudyn ((~)1.0.1): A daemon to control laptop power consumption via cpufreq and disk standby
[N] sys-power/cpufreqd ((~)2.2.1): CPU Frequency Daemon
[N] sys-power/cpufrequtils (002-r3): Userspace utilities for the Linux kernel cpufreq subsystem
Found 6 matches.
ahuemer@xeon ~ %

[vent83]

@alex.blackbit:
Well, from what I can see these are sadly only intefaces for the CPUFreq driver. This driver uses the Speedstep technology in case of my processor - and according to my knowledge this reads several fixed possible configurations for the CPU frequency/voltage from the ACPI and those standard configurations do not include an underclocked FSB option - that is why I cannot set it through the CPUFreq driver (or any tool using it).

I've heard about kernel patches which allow for example manual CPU undervolting - maybe somebody knows if these kind of patches also allow to underclock the FSB - in the general case - or in the case of my specific hardware?

[widan]

Is there a way to set the FSB frequency? And if there are several ways - which is the most official/supported way? Can it be done for example in some conjunction with CPU frequency scaling (like Speedstep) and undervolting?

FSB tweaking is specific to each motherboard, as you need to talk to the clock generator chip. There is no general way of doing that. There is (or at least was) such a driver in the kernel for nForce 2 chipsets for Athlon XP CPUs, but that's the only one I know of. And that one was quite hard to master, it was easy to get the machine locked up if you dropped (or raised...) the FSB too fast or too far.