Hello there. This is my first post on this site and am a recent member. I have enjoyed reading through many posts but am curious about something.

I am running a q9550 overclocked to 4 Mhz with liquid cooling on an EVGA 790i Ultra SLI board, and a brand spanking new EVGA GTX 260 Core 216 Superclocked I was wondering why various GPU tasks take anywhere from 2% to almost 25% of CPU? I have one now thats used over 14 hours of CPU time. WOW!!

The amount used doesn't seem to be predictable, so was wondering what the CPU portion of the workunit is doing to support the CPU. The amount of CPU time used by the time the workunit completes can be many many hours. I am curious but haven't seen a posting or any other information on the site that explains this. Any input welcome. Thx.

Hi Neil,

in short: the CPU has to "poll" the GPU, i.e. it's asking "are you ready yet?". Since the GPUs are fast, this has to happen a lot, otherwise the GPU goes idle. On Linux this just takes about 1% of a CPU core, but on windows the developers couldn't find a way yet to keep the GPU busy and to avoid this high CPU usage at the same time.

By the way, I took a look at your results and it seems ilke you're running both, your 8800GT and the GTX 260 and BOINC is switching between both in a rather uncontrolled manner. Or did you physically swap the cards that often during the last WU(s)? ;)

MrS

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Scanning for our furry friends since Jan 2002

Hey MrS, thanks for your response.

I have several computers at home. My main gaming system has/had 2*8800GT (512MB) which have been in and out of SLI mode. I've finally figured out that I'll be able to process more WU's if I don't run them in SLI mode.

The other day I bought and received 2 GTX 260 Core 16's. One of them is in my gaming system with an 8800GT, and my main home computer has the other GTX 260 right now. So I agree, my result stats could look a little wonky. My end goal is to have both 260's in my gaming system and the 2*8800GT's in my home system, so there would be a total of four GPU's reporting results.

Hope this helps.

Hope this helps.

Sure, I was just a bit curious ;)

MrS

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Scanning for our furry friends since Jan 2002

way CPU use only 0.90 of CPU ? instead of 0.98 ?

or way it use CPU !!!! and GPU is NOT HOT ((( is seem dos no work at all ((((
(I use 9800GTX+ and 2x 9600GSO )

way CPU use only 0.90 of CPU ? instead of 0.98 ?

Simply because it doesn't need a full CPU. Actually it needs only about 0.6 CPU (on Windows).

or way it use CPU !!!! and GPU is NOT HOT ((( is seem dos no work at all ((((
(I use 9800GTX+ and 2x 9600GSO )

If you are computing GPUGRID tasks, and get credit for them your GPU is for sure used. These tasks can't run only on a CPU...

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way CPU use only 0.90 of CPU ? instead of 0.98 ?

It does not use 0.90 CPU.

This is only a number to tell BOINC that the application uses less than 1.00 CPU core. It can be any number between 0.01 and 0.99 and the application will use the same amount of CPU, not the number shown in BOINC. The number only matters for BOINC to reserve CPU space for the application. With the current setting, BOINC will reserve CPUs for the GPU tasks as 0.90 x number of GPU's you have, e.g. 1=0.90, 2=1.80, 3=2.70, 4=3.60. The CPU is necessary to send data/instructions to and receive results from GPU. It also does the disk writing. You cannot just have a GPU only applciation. The GPU is a co-processor, not a dedicated processor. It needs a dedicated processor to feed it. BOINC can use up to 0.99 plus number of cpu cores you have for scheduling, e.g. a dual core can schedule up to 2.99 tasks, where anything over two is a cpu/gpu combination.

You need to look in windows task manager to see actual useage.

or way it use CPU !!!! and GPU is NOT HOT ((( is seem dos no work at all ((((
(I use 9800GTX+ and 2x 9600GSO )

More info is needed.

Does your boinc show CUDA devices and co-processors when it starts. Check message log. Post the lines here that show this.

What version o/s, boinc and nvidia drivers do you have ?

How many CPUs or cores do you have ?

Are you GPU's not in SLI mode ?

i test last time
on 9800GTX+ 178.24\ 2008 server x64\ boinc 6.3.14
Q6600@3300Mhz (http://www.gpugrid.net/show_host_detail.php?hostid=15470)
sesms it wokr only 12,705.89 but real time is 1 full day (((((((((( and take 8-10 CPU GPU_core temp =47 insted 62 in FAH
its run's with a 4x Rosetta@home core
||CUDA devices found
||Coprocessor: GeForce 9800 GTX/9800 GTX+ (1)

to day i test in same comp
6.4.1 \ driver 180.48 3x Rosetta_core and 1x grid...
win say that 1x grid take 19 -20 % of CPU (((((((((((((( GPU_core temp =62 same in FAH
and 5-6 % is free

23.11.2008 22:12:06||CUDA devices found
23.11.2008 22:12:06||Coprocessor: GeForce 9800 GTX/9800 GTX+ (1)

in other COMP 9550@3800Mhz http://www.gpugrid.net/show_host_detail.php?hostid=15460
i have test 6.3.19 \2008x64\ 178.24\ 2x9600GSO
4xRosetta_core and 2x grid..
grig wokrs 20,028.70\26,857.77 but rial time is wu take 28-38 hours ((((((((((((((((( GPU_core temp =45 \47 insted 60-62 in FAH
they take 2x9-10 % CPU ((((((((((((((((
|CUDA devices found
|Coprocessor: GeForce 9600 GSO (2)

NO SLI mode ! (MB asus P5K-E\Wifi )

Kodak, the format of your posts is horrible! Please, take a few minutes and make them readable. That would safe people who want to help you from getting head aches!

MrS

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Scanning for our furry friends since Jan 2002