While the FPGA is getting its share of the spotlight, commercial GPU farms such as the one pictured in this post are advancing in both size and number. The leading GPU farms use economies of scale combined with low power costs to solve blocks at a lower cost than any solo miner paying residential rates could ever hope for.
The operator of this specific mining farm posted the photo that enables its bond investors to do a visual audit, performed remotely, to help verify the assertion that 100 Ghash/s of capacity truly exists.
The recent difficulty threshold for generating bitcoins went from 1,508,590 to 1,733,208, representing nearly a 15% increase in just over 12 days. The difficulty readjusts every 2,016 blocks and this most recent adjustment happened when block 179,424 was reached. This increase is the biggest, in percentage terms, since June, 2011.
FPGA mining hardware units are shipping in larger quantities from some vendors though significant backlogs remain for BFL singles and the yet unreleased mini-rig.
FPGAs are an order of magnitude more efficient on electricity for the purposes of mining but GPUs are the workhorse for Bitcoin mining and are still competitive once considering hardware acquisition costs.
Those hardware costs been been dropping of late, especially for used hardware as operators sell off old hardware. They sell either because of their expectation that used GPU prices will fall further in the future or because the rising difficulty adjustments have sucked the margins from operating GPUs for mining.
The capitulation by the small miners suffering electric utility bill pain is benefiting these commercial operators whose facilities can accommodate further expansion that allows the overhead costs to be spread out over a growing number of producing rigs. The mining operation in the photo has grown its hashing capacity by 20% in the few weeks since the photo was taken, for example.
This strategy of continued expansion may result in gains in the short term but if hardware costs are amortized much past when the upcoming drop in the block reward is expected to occur (sometime around December), then these commercial operators could be facing a rude awakening.
The block reward drop will bring the yield from 50 BTC per-block to 25 BTC per-block. Many miners are hoping the resultant decrease in production will be offset with a rising exchange rate once the market recognizes that there will soon be a sudden drop in the supply of mined Bitcoins.
Because even used GPUs are still very useful to gamers looking to trade up from lower-end hardware, mining operators are able to take the more risky move of adding hardware yet with the worst case scenario being a relatively small level of losses if future plans must change.