cpu speed...what does it all mean?

[John Smith]

I had been under the impression ...probably wrongly..that the speed of a cpu
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 !
Can this be so..if so how come? The cpu is a Athlon XP 2500 Barton.
Thanks

 

[Mike T.]

I had been under the impression ...probably wrongly..that the speed of a
cpu 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 !
Can this be so..if so how come? The cpu is a Athlon XP 2500 Barton.
Thanks

Thermal throttling. Sides off, more airflow, but direction of airflow is
not cooling CPU as well. CPU heats up, MHz decrease. (thermal throttling)

Sides on, less total airflow, but CPU is cooled more efficiently as airflow
is in proper direction. Less heat, CPU MHz increases. -Dave

 

[John Smith]

Thermal throttling. Sides off, more airflow, but direction of airflow is
not cooling CPU as well. CPU heats up, MHz decrease. (thermal
throttling)

Sides on, less total airflow, but CPU is cooled more efficiently as
airflow is in proper direction. Less heat, CPU MHz increases. -Dave

--------------------------------------------
Thanks for that...you could be right about the reason for the change.
Further surprising info - did further observations....
....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 at 1093.
Then turned off the pc..then straight away turned on the pc and find temps
39 and 53 and
cpu speed now 1829!!...does that make sense?
BTW the spec of the 2500 Barton is 1883MHz.
Thanks.

 

[Paul]

--------------------------------------------
Thanks for that...you could be right about the reason for the change.
Further surprising info - did further observations....
...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 at 1093.
Then turned off the pc..then straight away turned on the pc and find temps
39 and 53 and
cpu speed now 1829!!...does that make sense?
BTW the spec of the 2500 Barton is 1883MHz.
Thanks.

You don't say what motherboard it is. Some motherboards, if they
think the CPU crashed while still in the BIOS, will declare
an "overclocking failure". Their recovery strategy, is to set
the clock to 100MHz the next time the computer is started.
Voila, 1100MHz core.

That doesn't explain how it got back to 166MHz bus clock again.
If the user modified the setting and saved it, that would get you
back to 166x11=1826MHz or so.

So I'd say the computer thinks it has crashed, and the BIOS
is reducing the clock the next time the computer POSTs. The
bad part is, sometimes the failure that is occurring, is
early in the BIOS initialization sequence, and there is nothing
the user can do to fix it. (I would want to Google on the motherboard
model number, to see if other people complain about "cold start"
problems.)

Sometimes, if this happens to a lot of users, the motherboard
maker will modify the BIOS to do a better job at initialization.
Flash upgrading to the latest BIOS might be one thing you can
try.

AFAIK, there is no throttle on a Barton. There is a thermal
diode, and if the motherboard has a monitor chip connected to
the diode, then the motherboard may be able to switch off
the ATX supply if the processor gets too hot. On some
Asus boards, the monitor chip is a tiny 8 pin device from
Winbond.

Paul

 

[John Smith]

You don't say what motherboard it is. Some motherboards, if they
think the CPU crashed while still in the BIOS, will declare
an "overclocking failure". Their recovery strategy, is to set
the clock to 100MHz the next time the computer is started.
Voila, 1100MHz core.

That doesn't explain how it got back to 166MHz bus clock again.
If the user modified the setting and saved it, that would get you
back to 166x11=1826MHz or so.

So I'd say the computer thinks it has crashed, and the BIOS
is reducing the clock the next time the computer POSTs. The
bad part is, sometimes the failure that is occurring, is
early in the BIOS initialization sequence, and there is nothing
the user can do to fix it. (I would want to Google on the motherboard
model number, to see if other people complain about "cold start"
problems.)

Sometimes, if this happens to a lot of users, the motherboard
maker will modify the BIOS to do a better job at initialization.
Flash upgrading to the latest BIOS might be one thing you can
try.

AFAIK, there is no throttle on a Barton. There is a thermal
diode, and if the motherboard has a monitor chip connected to
the diode, then the motherboard may be able to switch off
the ATX supply if the processor gets too hot. On some
Asus boards, the monitor chip is a tiny 8 pin device from
Winbond.

Paul

------------------
Many thanks for explanation and info...sounds plausible.
Yes, the board is Abit NF7-S..and I haven't upgraded or
touched the BIOS since pc new which was Feb '04....bit scared to fiddle with
BIOS
Further info...from cold start this am and with sides on the figs are
25C, 46C and 1831MHz
Further....don't know if this co-incidence or something to do with it...but
during the last couple days the pc on switch off has been restarting itself
....viz
when I switch it off in the normal way...click Start/Turn off computer, it
goes through the usual routine...Windows is Logging Off...Windows is
shutting down...then at the point of clicking off it seems to do a double
click and starts up again!
I changed the settings....
My Computer - RtClk- Properties
Advanced tab
Start-up and Recovery - Settings button
System Failure:
untick Automatically restart
...and even now sometimes it automatically restarts - sometimes it doesn't.
Thanks.John

 

[Paul]

Many thanks for explanation and info...sounds plausible.
Yes, the board is Abit NF7-S..and I haven't upgraded or
touched the BIOS since pc new which was Feb '04....bit scared to fiddle with
BIOS
Further info...from cold start this am and with sides on the figs are
25C, 46C and 1831MHz
Further....don't know if this co-incidence or something to do with it...but
during the last couple days the pc on switch off has been restarting itself
...viz
when I switch it off in the normal way...click Start/Turn off computer, it
goes through the usual routine...Windows is Logging Off...Windows is
shutting down...then at the point of clicking off it seems to do a double
click and starts up again!
I changed the settings....
My Computer - RtClk- Properties
Advanced tab
Start-up and Recovery - Settings button
System Failure:
untick Automatically restart
..and even now sometimes it automatically restarts - sometimes it doesn't.
Thanks.John

That is an even worse problem. I've seen posts from people with similar
problems, but no definitive cause. I don't have any good suggestions
for that, because I have no idea what is doing it. That could be
a driver that is crashing right at shutdown, so think back to whatever
drivers or Microsoft updates you've done lately. It could also be
some kind of hardware problem ? Time to start Googling I guess...

http://aumha.org/win5/a/shtdwnxp.htm

Paul

 

[John Smith]

That is an even worse problem. I've seen posts from people with similar
problems, but no definitive cause. I don't have any good suggestions
for that, because I have no idea what is doing it. That could be
a driver that is crashing right at shutdown, so think back to whatever
drivers or Microsoft updates you've done lately. It could also be
some kind of hardware problem ? Time to start Googling I guess...

http://aumha.org/win5/a/shtdwnxp.htm

Paul

--------------------
OK, TVM...
Thanks for the useful info.
Further info...
Just checked the following when sides on and sides off via cpu-z:-
with sides on first (and sides off)
Core speed - 1830 (1094)
voltage - 1.648 (1.664)
Multiplier - 11 (11)
FSB - 166.4 MHz (99.5)
Bus Speed - 332.7 MHz (198.9)
Again...does that make any sense to you?
Thanks again