Bitcoin Currency and GPU Mining Performance Comparison
GPU Performance per Dollar and per Watt
The most basic information (and the most fundamentally important) we can provide is the Mhash/s of each graphics card we are testing. For dual-GPU graphics cards we ran two instances of our poclbm kernel under the GUIMiner client and rates were added together to get a total maximum output per card.
Again, the first thing we notice is just how poorly the NVIDIA cards are stacking up against the AMD offerings. If you look at the GeForce GTX 580, a $469 graphics card, against the Radeon HD 6850 at $209, the AMD card still has a commanding 35% performance advantage. The Radeon HD 5830, which can often be found for around $100, is easily one of the best deals for Bitcoin mining and is even faster than NVIDIA dual-Fermi-based GTX 590 card! The dual-GPU AMD cards even more impressive and we can see from the HD 6990 that the Cayman architecture brings a lot to the table as it can pull about 340 Mhash/s for each GPU. The overclocked ARES card takes the top spot with over 800 Mhash/s (a 38% boost over stock settings for that card).
Also take note of the AMD A8-3850 APU - with a Mhash/s rate of 80.7 it is actually computing faster than the GTX 560 Ti, the GTX 460 and even the dual-GPU (but aging) GTX 295. It looks like if you want to maximize your Bitcoin mining experience building a system around an AMD APU could be a good way to supplement discrete cards.
Sure, you can build the fastest super computer if you have an unlimited slush fund but what is the most cost effective way to mine for Bitcoins?
The larger bar the better for your wallet here and we can see why the Radeon HD 5830 cards have been flying off Newegg's shelves! With a current rate of 1.544 Mhash/s/$ it comes in well ahead of anything from NVIDIA and about 20% better than its closest competitor in our testing, the HD 5750. No NVIDIA card even comes close the AMD allotment here as even the A8-3850 is able to best the GeForce lineup. Keep in mind in that case as well you are getting the GPU computing power for mining as well as a quad-core processor as well increasing the overall real-world "value" of the part.
Even though the ARES card and the HD 6990 took the top performance rankings they come up short to the less expensive Radeon HD cards like the HD 6850. It appears that as with gaming performance, Bitcoin mining performance sees the law of diminishing returns in GPU price increases.
If we take cost out of the picture and you just want to build a more power efficient Bitcoin miner, what cards will make the most sense?
Kind of surprisingly, the dual-GPU Radeon cards make the biggest splash here with the overclocked ARES card (that used 50 watts or so more power than the base ARES settings) taking the overall crown at 1.584 Mhash/s/watt. The HD 5970 and HD 6990 also gathered closely to the base ARES settings to show us that even though they user more power, the single card scenario definitely helps with efficiency in this case.
For single GPU cards the Radeon HD 5830 is the winner yet again making it the easy choice for the best card (so far) for Bitcoin mining enthusiasts. NVIDIA cards which have had the stigma of being power hogs for years now seem to showcase that drawback substantially here.