[ltp] kernel detecting incorrect processor speed

[Lai Zit Seng]

On Fri, 8 Sep 2000, Paul Hahn wrote:

> Yes. This is so because of the IBM bios. You can control the speed of
> all laptops, and thus their power consumption, by using the Fn+F9 key,
> or whatever the water spigot character is over on your T20. This value

There is none on my T20. I've seen that key on my older ThinkPad, but not
on my current T20.

> is only determined once in Linux, at boot up when bogomips is run. So
> if you change it after you boot, or plug the power cable back in
> (which automatically speeds up your proc) you will have to reboot

Well, I did nothing to suggest that the CPU speed should change. Ie, I was
always on battery. I always shutdown/power-off then boot up. Without
changing any settings. Each time I get a different CPU speed reported in
Linux. 148Mhz and 547MHz are the most "popular" values that appear,
although many other speeds in-between also got reported. This is a 700MHz
T20. That's why I'm puzzled.

I can understand that if I warm boot... maybe some prior event had caused
the CPU to run faster, or slower. But no... always cold boot and still
different CPU speeds!

> inorder to "see" the change. The proccessor is running faster however,
> you will just not be able to see the change on your utilities because
> they use bogomips to determine this value, and since it only runs once
> will not report the change. In Winblows you can use the Ibm utilities
> to control the default values for whether or not your notebook slows
> down when on battery or not. Forcing to stay on full flow will solve
> the "problem" of it going slower on battery. This is a issue on all
> IBM laptops, not just speed step, although it may compound the
> confusion.

And of course, on AC power... I do get a consistent cold-boot CPU speed
reported at 696MHz (which is close enough to the supposed 700Mhz).

Regards,

.lzs

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