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Re: AMD cpu slows down (I think)



Hi Trevor,

On Sat, 30 Oct 2004 13:18:47 -0300, Trevor Smith <trevor haligonian com> wrote:
> My situation: I have a Compaq Presario 2197CA, AMD Athlon XP-M 2800+ CPU. With
> Fedora Core 1, no problems on AC or battery power. After upgrade to FC2 with
> kernel-2.6.5-1.358, originally no problem (I don't recall). But at some point
> I updated the kernel to kernel-2.6.8-1.521 and possibly then, possibly
> because of some other "upgrade" my computer slips into a different mode when
> on battery power.

I have a Compaq R3000Z with an Athlon64 that is very similar to your
R2197.  You might look at the archives of the LinuxR3000 mailing list:
http://quanta.homeip.net/mailman/listinfo/linuxr3000  While not
directly applicable, there is some discussion about frequency scaling
with the k8 driver.  I'm using the k8 driver with powernowd, and
frequency scaling works great.

[snip]
> After my long ramble, 4 questions:
> 
> 1. am I correct in my assessment of the situation, do you think?

Not sure, but probably on the right track.  Look at the files in
/sys/devices/system/cpu/cpu0/cpufreq/  Specifically cat the files
scaling_available_frequencies and scaling_governor to see what
frequencies you can run and what governor you are running.  I know if
I boot up on battery power, my laptop cuts off the highest frequency
setting.  Also, check that you are running cpufreqd or powernowd or
something of the like.  If you are using one of these, you
scaling_governor should read "userspace" to use them.

> 2. how could anybody want to use a system that is struggling to update windows
> and such, no matter how much longer it made their batteries last?

Certainly the performance you are describing is not good.  With
scaling, your processor should idle at a lower speed and then increase
speed when it needs to do work.  This prolongs battery life and saves
power and heat as your processor can relax when it isn't doing
anything useful.

> 3. is my problem more likely the result of poor/nonexistent graphics
> acceleration which causes the CPU to do graphics work as well as system work,
> thus when the CPU is slowed down, graphics slow down?

This could be true.

> 4. how can I turn this d*** Powernow thing off?

If you really want to turn it off, you can do this as root:
echo "performance" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
This will cause you cpu to always run at the highest available
frequency.  Now, this frequency could be lower if you are on battery,
which is what I see on my laptop.  The best thing is to use a
governor.  Powernowd is pretty good, and it's simple.  You can get it
from http://www.deater.net/john/powernowd.html  Do some looking around
in /sys/devices/system/cpu/cpu0/cpufreq/ and report back what you
find.

Jonathan


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