Prime95 - summer edition
 

The hot summer is just a few months away ;) .
Some of us know how hot it gets when you let Prime95 run 24/7 in a room without air conditioning. No metter how good the fans are. Slowing it down a bit will help the CPU stay cool. When I downloaded the 21.? version's source code (long time ago...) I modified it like this: a new edit box "Sleep in ms/iteration" in the "Preferences" dialog and just called a Sleep() after each LL iteration. A value of 20-30ms/iteration keeps my CPU at about 70%. When it's cold enough (like now) I just enter 0 and it works at full speed.
Do you think it would be a good thing to have this feature implemented in the official version ?

Very interesting. Could this have application for laptops? I don't own one, but I've heard laptops have heat problems but worse. Does anyone do LL on a laptop?
A touch of irony here: A throttle mechanism for some of the most highly optimized code I've ever used. :?

I'll add it in 23.3

I like the idea of this option, but I think it might be better if it were a percentage of CPU time rather than ms/iteration. That way, when you work on an exponent of a different FFT size, the actual percentage of CPU time that Prime95 uses won't change like it would if you did ms/iteration.

Boy that is a good idea!

I try to run Prime95 on my wife's 1.5GHz laptop but it cycles the fan too much... I could probably set it to 25% and it would run (slowly!) just fine...

Anything is better than nothing!

My only concern is if the power/non-power cycles are too large they will heat/unheat the CPU causing thermal stress, but if the duty cycle is implemented rapidly, like how an electronic speed control controls a motor (1000s of Hz) then it would be just perfect...

Scary thought... What if someone tries a 25% duty cycle on a P75 laptop! :)

I vote we give this feature a cool name, like flava-cycle®... :)

Well as flava implemented it, the sleep function was called after every iteration which is essentially in 10's of milliseconds. Now some chip expert tell me here if this will cause thermal stress.

I guess George could make a smarter implementation where sleep is called more frequently? That will cause less stress!?

Laptop
 

That is very interesting idea. I do run Prime95 on a P4 laptop 24/7. The only time it doesn't run is when I'm running off of the battery. The stop when on battery feature works great.
What I'm wondering is if implementing this type of feature will cause these new mobile processors to keep changing their speeds - i.e. SpeedStep, etc. When I run Prime95 my laptop is at 1.8GHz, if I stop it it will go down to 1.2GHz. I wonder if cycling will cause my laptop to go from 1.8GHz to 1.2Ghz and back.

I use a Winbook 2.4 GHz P4 laptop with 512 MB of RAM. I don't have many problems with it getting REALLY hot as others describe. How will this new CPU percentage function change the amount of time it takes to do a test? If it will slow it down, I don't want it.

[quote="Jwb52z"] How will this new CPU percentage function change the amount of time it takes to do a test? If it will slow it down, I don't want it.[/quote]It will of course slow progress in proportion to the extent you use it. If you add a 20 ms break per iteration and the iteration time is 80 ms, the test will take 25% longer. (Assuming I've understood flava properly!) But for some people that will mean using their laptop for GIMPS where they wouldn't otherwise have done so, meaning more progress overall. And no one will force you to use it!

I think there should be a choice to do it either way. I'd rather not have to mess with CPU usage to use the program.

Oh yeah! I'm sure there would be a choice and by default this option would be turned off. So unless you want otherwise your CPU will run 100%.

Turned off by default would be good, as I for one don't plan to ever use it.

That's what Delta and Vantech/Sunon fans and GOOD heatsinks are FOR.

8-)

I thought that is what waterblocks were for :).

Water cooled is nice, but I can build a complete Athlon cruncher *system* with good-enough air-cooling to survive summer heat fot the cost of that water-cooling system.

9-)

I'm a little confused by all the responses since this one: [url]http://www.mersenneforum.org/viewtopic.php?p=3344#3344[/url].

Now that summer is upon us, I'd like to see George procede with this mod in its simple form of a sleep call/iteration; if he is still willing. :mellow:

It's in 23.3, according to undoc.txt (& the corresponding part of the help file) although it didn't make the whatsnew.txt.

[quote]If you are running on a laptop or in a hot room and you want to slow the program down to reduce heat, then you can add this line to prime.ini:

Throttle=n

where n is the number of milliseconds to sleep after each iteration.[/quote]