CPU speed - why does it change?

Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

Threaded View


Not really an overclocking question but knowledgeable members might be able
to offer help :-)

I'm not too familiar with the workings of cpu...so I'd be glad for any
comments/advice ref the following.

Abit motherboard NF7-S and Athlon XP 2500 Barton cpu

Have just discovered I seem to be working with two different CPU speeds...

1.about 1830MHz when the sides of the computer are ON (the Barton's spec is
1883MHz so thats ok), and
2. about 1075-1095MHz when the sides are OFF

I had been under the impression ...clearly wrongly..that the speed of a
cpu under normal use was pretty well constant?
Made a note in Motherboard Monitor (MBM) of the cpu speed with sides of
the box OFF = 1094 MHz...with sides ON this jumps to 1796MHz !
Is that what could be expected, and if so how come?

And further...from start up and with sides off and cpu speed showing 1093MHz
and board
temp 29C and cpu temp 42C
I then put back on the sides, and, after 40mins temp rose to 36C and
48C but cpu speed still showing 1093!?
Then turned off the pc..then straight away turned on the pc and find temps
39 and 53 and cpu speed now up at 1829!!...does that make sense?

...and lastly Just checked the following when sides on and sides off via
with sides ON first (and sides OFF)

voltage - 1.648v (1.664)
Multiplier - 11 (11)
FSB - 166.4 MHz (99.5)
Bus Speed - 332.7 MHz (198.9)
Core speed - 1830 MHz (1094)

Again...does that seem reasonable?...Its baffled me :-)

Any help would be appreciated.

Re: CPU speed - why does it change?

On Wed, 10 May 2006 15:22:21 +0100, John Smith wrote:

Quoted text here. Click to load it
The speed change is obvious. You have some software that is changing the
FSB speed. The CPU speed is muliplier x FSB speed. So 11x99.5= 1094MHz and
11x166.4=1830MHz. Why it happens when you take the side cover off is
either a coincidence, or your software is monitoring the side cover switch
(if your case has one) and is lowering the speed (this isn't likely
afaik). Or it could be something else altogether.

Want the ultimate in free OTA SD/HDTV Recorder? http://mythtv.org
http://mysettopbox.tv/knoppmyth.html Usenet alt.video.ptv.mythtv
My server http://wesnewell.no-ip.com/cpu.php
HD Tivo S3 compared http://wesnewell.no-ip.com/mythtivo.htm

Re: CPU speed - why does it change?

Quoted text here. Click to load it
OK, Thanks.
I understand about FSB x Multiplier...its the why the devil it changes
between case sides on and off  that's the puzzle.

Site Timeline