CPU load in GPU mining

[Oldgamer]

I use bfgminer 3.0.0 with Windows 7 and noticed that task manager shows CPU E-240 APU load constantly floating in between 30-90% and all this load related to bfgminer only. Sure, I use slow processor (look this combo: http://www.newegg.com/Product/Product.aspx?Item=N82E16813157324), but I use only one 7850 card which mining speed varies from 165 to 320 Mh/s (most of the time around 225-245). What makes me wonder, that I remember, when I just installed Windows and first run miner CPU load was very low, but now it is kinda high to my taste. I do not want CPU to be a bottle neck. I can not understand why CPU load became higher. The only thing is now my command line includes some more parameters. Can this affect CPU load so much?
It is not like it bothers me a lot, but I curious to know.

Thank you for any info.

BTW, 2 GB RAM installed,GPU clock set to 1000.
GPU temperature: 69-72
Fan: 41-56%


Parameters:
--intensity 11 --vectors 1 --worksize 256  --lookup-gap 0 --thread-concurrency 0  --shaders 0 --gpu-engine 1000 --auto-fan --gpu-memclock 900  --gpu-memdiff 0 --gpu-powertune 0 --temp-cutoff 90 --temp-overheat 85 --temp-target 72 --api-port 4028 --expiry 120 --gpu-dyninterval 7 --gpu-platform 0 --gpu-threads 2

[os2sam]

If your mining bitcoin you have a bunch of stuff in there you don't need.  Trim your command line down to just what you need instead of having that stuff set to "0".

Also if your Bitcoin mining Intensity of 11 seems high to me, but I don't know anything about 7xxx GPU's either.  I would set Intensity to 9, that in and of itself may be effecting your CPU Utilization and hash rate.

Sam

[Oldgamer]

Thanks, I will test it with trimmed line, I just found the line I use on forum as optimum line for 7850 card.
When I run miner with no parameters at all it loads GPU only for about 50-60% (do not remember now exactly).

[TheSpiral]

SHA256 (BitCoin) mining will crank up the CPU a little bit in cgminer/bfgminer on newer Catalyst drivers. You could do a couple things:
Downgrade driver version (will affect hash rate, either for the better or worse).
Change priority by adding "start /low" at the beginning of the command line, should lower CPU usage a little bit.

[crazyates]

SHA256 (BitCoin) mining will crank up the CPU a little bit in cgminer/bfgminer on newer Catalyst drivers.

Not quite true with 13.4. I will agree that a lot of people have issues with 13.4, so 13.1 would be a safer bet.

And yes, you do have too much in your options. Try trimming it down to this:

-I 7 --auto-gpu --auto-fan --gpu-fan 25-90 --gpu-engine 500-1000 --gpu-memdiff -150 --temp-target 72

[Oldgamer]

crazyates,

I used the parameters you posted and CPU load became drastically better. Now it is only 1-4%. With intensity 7 speed was a bit lower (but in reality it is really hard to verify) I think, I made it 9 and now it is probably same if not even better than before (again it is really hard to verify, cause it is not a constant value and floating).
Actually measuring hashing speed can be an object for a special research. I think that in reality it can be only measured as an average for long enough time, but again, I do not know how to do it.

Thanks

Edit:
P.S.
I actually find out now, that intense value is what can make huge difference in CPU load. When I changed it from 10 to 11 CPU load increased from 1-4% to floating in between 45-85%. All other parameters did not change CPU load.