I have recently bought an asus laptop based on f5sl model and I have installed Slackware 12.1 on it. The hart of the machine is Core 2 duo cpu and it uses SIS chipset modified by ASUS.

For the last few days i was trying to enable SpeedStep functionality. None of the speedstep modules haven't worked (for each of them i have received message: "FATAL: Error inserting ...: No Such Device"). At the end I've managed to activate frequency scaling with acpi_cpufreq module in a bit unusual way (or maybe not). First time I've tried to insert acpi_cpufreq module I've received familiar message: "Error inserting acpi_cpufreq module ... No Such Device". But after I've issued the same command again everything have worked as it should. So i have solved the problem by inserting cpufreq module in the initrd image and calling it from startup script also. This is not very elegant but it works.

I would like to know if somebody have had the same problem like me and whether he solved it in a not so complicated way? Also i would like to know what is the reason for such behavior and is this a good solution at all (good for my CPU)?

Have you tried looking for a guide for your specific laptop? Try on http://www.linux-laptop.net/
Second, I remember there should be some option to pass to the acpi-cpufreq module to force its insertion, but I'm not sure.
Third, it's better to verify the powersave capabilities of your cpu first, you can do this by looking at the file /proc/cpuinfo, that gives some information and, at least on my system, says that the CPU has some power management capability

The description says:

So this is the correct driver for Intel Speedstep. I don't know why it requires two modprobes. If you compile your kernel yourself you can compile it in. As you see above you also need the ACPI->Processor support.

acpi-cpufreq is the correct module name though (not acpi_cpufreq)

@clvic
First: of course, I have tried on both http://www.linux-laptop.net/ and http://www.linlap.com/ but without success.
Second: if you could remember how to force insertion, that would be nice (even if i decide not to exploit it it is something one should be familiar with). As I remember there was some lilo option to instruct kernel to run certain options at boot. I should take a look at lilo's documentation.
Third: output from /proc/cpuinfo shows that my CPU has Enhanced SpeedStep capabilities (it is "est" flag in the flags list):
fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts pni monitor ds_cpl est tm2 ssse3 cx16 xtpr lahf_lm

@Ilgar
The idea has been to set up as much as possible without recompiling the kernel or compiling the new one. What you've suggested could solve the problem but I am trying to avoid that solution.

@keefay
Indeed it is, but if you modprobe acpi_cpufreq it calls the right module acpi-cpufreq.ko, so I don't think this causes problem. In fact I have tried to modprobe acpi-cpufreq and I have got the same problem. Nevertheless the correct syntax is as you noted and should be used.