laptop slowdown

[nomadicus]

I have a Dell Inspiron 5100 with a true P4, 2.53GHz, not an Mobile or a Centrino, etc.
Based on the documentation, I don't think the hw adjusts the clock speed when the room temperature rises (no a/c where I was staying out west for a week)
The iteration times went up and down (nothing was running, I made sure of that) from a low of 0.083 up to 0.091. Can the clock itslef slow down as the ambient air temperature rises?

[Xyzzy]

No, it can only throttle the CPU, and if that happened your times would really slow down a lot...

The variation in iteration times you see might be due to things running in the background or maybe there is some paging/swapping going on...

Set the output to 100,000 iterations per line (Or higher!) and see what you average...

[trif]

The throttling is in the chip itself I think, and it certainly should be in the P4. The first step down on my Celeron 466 is to 400, which is approximately the same percent that you're seeing as the variance on your iterations times.

[Xyzzy]

I think Trif might be right...

http://www.mersenneforum.org/viewtopic.php?p=2582#2582

However, in On-Demand mode, the duty cycle can be programmed from 12.5% on/87.5% off, to 87.5% on/12.5% off in 12.5% increments.

[nomadicus]

Thanks Trif/Xyzzy,
What I observed fits very well with the 12.5% off duty cycle. I have iterations set at 10,000 which displays the iteration times every 2hours+. I take all that to mean it switched from 100% down to 87.5% (or more) and back over a long period of time.
That is really great that the P4 protects itself up to 135C.
I wonder if the AMD XP1700 (and faster) do this?
In terms of heat management, maybe the extra cost, in general, of a P4 is worth buying over the AMD (I'm an AMD fan, except for prime95 work, but nuggets like this may will sway me towards P4's).

[trif]

Originally Posted by nomadicus

Thanks Trif/Xyzzy,
What I observed fits very well with the 12.5% off duty cycle. I have iterations set at 10,000 which displays the iteration times every 2hours+. I take all that to mean it switched from 100% down to 87.5% (or more) and back over a long period of time.
That is really great that the P4 protects itself up to 135C.
I wonder if the AMD XP1700 (and faster) do this?
In terms of heat management, maybe the extra cost, in general, of a P4 is worth buying over the AMD (I'm an AMD fan, except for prime95 work, but nuggets like this may will sway me towards P4's).

AMD has a diode that can be used to signal the motherboard that the chip is too hot and the system should shut down, but it doesn't have the throttling feature. I buy AMD for my desktop systems (price/performance can't be beat), but my laptop is an Intel chip. I think the throttling is absolutely essential in a laptop because laptop fans are notoriously flaky, and the throttling will protect the chip while still leaving the system usable. The fan on my laptop is busted, and while I can keep it running full speed for Prime95 by putting a secondary fan behind the vent, I can still use it as a laptop away from the extra fan, although it will throttle down.

So I'd go by the demands that will be made of the processor. If you need absolute thermal protection, buy the Intel. If you don't then the chance of having a freak accident with an Athlon and having to replace it doesn't outweigh the price differential that you'd have to pay for equivalent performance on the Intel (not counting SSE2 friendly apps like Prime95).

[markhl]

Originally Posted by nomadicus

I have a Dell Inspiron 5100 [text deleted] (no a/c where I was staying out west for a week)

But you were staying in a room with a refrigerator, right? :-)

[nomadicus]

Originally Posted by markhl

But you were staying in a room with a refrigerator, right? :-)

I helped stock my daughter and husband's frig with all kinds of stuff. yum! :) And you know what? My grandson was born shortly after. They are all doing great :D and, after about 2 weeks, I'm glad to be home tonight. 8)