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I've read many times over a long period of time that GPU will win out against CPU every time if you use hardware of a similar tier/age. However, i've been toying around today with some FTC mining and noticed what appears to be the opposite.

My rig:

  • i7 4770k (no overclock currently)
  • 570 GTX Twin Frozr
  • 16Gb RAM + SSDs

I'm mining using the latest versions of Pooler's CPU miner + CudaMiner.

When i mine with the CPU on 4 threads (no hyperthreading), i get 67kh/sec with an increase of 64w power, measured using Asus AI Suite (motherboard software).

When i mine with the GPU, it runs @ 71% average load (measured in GPU-Z), gets 145kh/sec and the power from this rise should be around 151w, according to official and unofficial power spec/stats.

By my maths, i make this out to be roughly:

  • CPU - 1.05kh/w
  • GPU - 0.9kh/w

The kh/sec numbers also seem similar to other numbers i've read for my hardware, such as forum posts and this list - https://litecoin.info/Mining_Hardware_Comparison

I think i've done a decent amount of testing here, but i'm sure i must have made an error somewhere along the line. But so far, my numbers indicate that while the GPU gets more per second, it gets less per watt... thus, less cost efficient. I know i'm using Nvidia, which is less efficient for mining than AMD, generally, but these numbers go against everything i've read before now.

Can anyone explain this, or dispell my numbers? I'd love to work out what's going on.

Cheers.

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  • I can't judge the numbers so I just post this as a comment: You didn't consider initial hardware costs. Also there could be some nonlinear scaling effects (running multiple GPUs should be easier than multiple CPUs).
    – jnnk
    Nov 29, 2013 at 16:32
  • I guess you're right on that point, but everything i've read always stated that CPU was pointless to even consider, even on currencies other than BTC. If i'm right in thinking that this is working as i think it is, then i'll continue to do it until i bother creating myself a true mining rig. (Which, of course, will be all about the GPUs!) Edit - I'd like to add that by "worth it", i mean power efficiency, which is what i gathered from my previous research/reading. Simply using existing hardware rather than taking the cost of investing in more hardware into account.
    – Gary Morris
    Nov 29, 2013 at 16:58

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The problem with your math is, that nvidia is far away from being optimal for GPU mining. If you would compare your CPU with an "older" ATI graphic card like my HD 6870 (about 150$) with max TDP 200W you would surely come to the opposite conclusion. I am mining with that card at ~280 to 300 kh/sec on average. Well I did not measure the extra power usage while it is on 100%, but it cannot be more than 150 Watt, since max usage is 200W. Besides: it runs really steady on 100% GPU load (measured with gpu-z) and drops only sometimes to 99% for a second. Not to mention that nowadays cards can get the double amount of kh/s.

I hope I could help you a bit. If you plan to invest into a new/second graphic card then you should go for ATI.

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