Question about feeding the GPU

I've currently got an i7-2600k running at 4.1 GHz and a slightly overclocked GTX-570. The GPU is running two WUs at a time and each WU has 5% of a CPU core dedicated to feed it (out of 4 physical and 4 hyperthreaded cores). The CPU runs at 100% 24/7 and the GPU runs between 90% and 95%. My question is should I dedicate a larger percentage of the CPU to feed my GPU to maximize output? If so, what would the more experienced crunchers recommend? I'm currently stuck around 37,000 RAC and would like to see if I can do anything to increase my RAC even further.

http://setiathome.berkeley.edu/show_host_detail.php?hostid=6421575

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AFAIK that percentage is just indicative -- the programme will use as much (or as little) CPU as it needs to service the GPU --

AFAIK that percentage is just indicative -- the programme will use as much (or as little) CPU as it needs to service the GPU --

Correct. Only when the sum of percentages of all concurrently running GPU tasks reaches 100% will one CPU (core) be reserved for feeding the GPUs.

Gruß,
Gundolf

So just leave it be and be happy with 37,000 then?

Yeah, what's wrong with that? (I would never OC a GPU!).
I, delebetatly clock down GPU- core and - memory speed, makes little difference on throughput, (I hate the word RAC) and I want reliable results,
not just fast..............!

It is about scientific calculations, so they've to be exact, very
exact, that where CUDA and OpenCL,comes in :), speeding this up.
Also, the new AVX-supported CPU's, like core I3 (XXXX)/I5-XXXX and I7- 2400/3730/50 etc.

Yeah, what's wrong with that? (I would never OC a GPU!).
I, delebetatly clock down GPU- core and - memory speed, makes little difference on throughput, (I hate the word RAC) and I want reliable results,
not just fast..............!

It is about scientific calculations, so they've to be exact, very
exact, that where CUDA and OpenCL,comes in :), speeding this up.
Also, the new AVX-supported CPU's, like core I3 (XXXX)/I5-XXXX and I7- 2400/3730/50 etc.

I only overclocked my GPU to the same settings as the factory overclock (they call it superclocked) model. I'm not pushing it harder than that. I do have errors, but right now it's 3 WU's in the last three weeks for that GPU. I think that's acceptable considering that on average my GPU goes through 400+ WUs per day. I'd definitely scale it back if it was erroring out more often.

You do realize that factory overclocked cards use better/more reliable parts than they're lesser clocked cards? Factory overclocking doesn't guarantee
that the card will be 100% reliable for Seti calculations. They run they're cards for gamers not scientific calculation.

I have Palit 460 that will throw errors on Seti units 4 to 5 times a day
at factory settings. Under clock the memory from 2000 MHz to 1905 MHz and it's
100% reliable. That's still way faster than reference card specs but under factory settings. Reliability is better than fast with errors.

Hi Irok

My setup is similar to yours (i7 2600K overclocked to 4.5Ghz on air with an nvidia 580). On 64bit Ubuntu 12.04 linux.

The i7 is an interesting beast as its 8 virtual cores, 4 real ones. This allows i7 uses to do something quite unique as far as CPU/GPU computing goes.

Core goals for CPU crunching is to use up to 100% of all cores to crunch (assuming the CPU has appropriate cooling) and ....

Core goals of GPU crunching is to crunch as many GPU work units as the GPU memory can handle while allowing the PC system user to use the graphics ability of their machine without degradation to the 'user experience'.

On the GPU front for me that meant running just 2 work units on it at a time. This is primarily because I play games on the system, as well as use it for normal office/web tasks. (Running 3 work units causes runtime issues with graphics games as graphics memory became contested resulting in GPU Seti work unit errors).

Now we come to the i7. The CPU must keep the data communication with the GPU occurring as quickly as possible with as much data as required. This is where the i7 works well ..... I have seti configured to use 50% of my CPU - that is 4 cores. But why just 4 when I have 8 virtual? Simply that by increasing it past 4 results in longer work unit processing times with very little RAC advantage.

The operating system will schedule each CPU work unit on each of the 4 physical cores. Some will now argue that these 4 cores may not be operating at 100% all the time. Well, great! Your operating system needs some space to do other things besides seti - so the system still remains fluid and responsive to all tasks - including seti.

Now this is also where the virtual cores come in. The operating system thinks there are 8 cores and will assign 'GPU data feeding' tasks for the GPU to one, or more, of the virtual cores not running the seti cpu task. This ensures that fluid scheduling is given to the 'quieter' seti cpu core and allows for the GPU to get the workload communication it requires.

This ends up being the best of all 3 worlds:

1) The real CPU cores being worked very hard
2) The GPU running efficiently - with maximum communication to the CPU
3) The PC itself remaining fluid for user interaction (a core goal of 'running seti in the background')

If you look at my stats atm they dont look great at around just 6000RAC, but thats with the pc running for only 3 to 4 hours a day atm. - so if it was run 24/7 it would be around the 35K RAC mark.

Anyway thats just my 2c worth. :)

Cheers

Mark
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Should be quite a bit more with 2600K and 580.
Just for comparison, my i7 920 (oc @ 3.2GHz, HT off), GTX 570 (stock), Linux, was doing between 35-37K RAC (not right now, since I'm doing E@H).
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My guestamate was worst case scenario, it could be as high as 50K :)

Cheers

Mark
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Thanks for the info. Unfortunately I installed the 0040 bios update on my DZ68BC Intel board and knocked out the overclocking (this bios update either does that or bricks the motherboard so I guess I'm lucky). I usually set the CPU to use 75% of the cores when I game and then switch it back when I'm done. I haven't seen any improvement when I run games with fewer than two cuda units going at the same time but I tend to play older games anyways. I'm averaging around 36k per day and I'm going to see what happens when Intel finally gets off its butt and releases a bios update that fixes what it broke. Their only action so far is to remove that update from their download page.
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