Product Comparison

Name Technology Ship Date MH/s $ (qty 1) $ (qty 10) W MH/$ (qty 1) MH/W
X6500 Spartan6 Now 360 580 550 20 0.574 18
Icarus Spartan6 2012-02-15 360 569 N/A 19.5 0.63 18.46
ZTEX USB-FPGA Module 1.15x Spartan6 2012-02-29 190 414 390 8.5 0.46 22.35
rph Spartan6 N/A, DIY 180 175 175 8 1.03 22.5
ATI Radeon HD 6870 GPU (for comparison) GPU Now 275 175 175 150 1.57 1.833

Last Updated: 2012-01-25. For the latest product information, please check the forum.

Bitcoin in a Nutshell

Bitcoin is a peer-to-peer currency based on public key signatures and an ingenious double-spend-prevention mechanism based on a cryptographic hash function (SHA256). Nodes in the Bitcoin network are rewarded for finding x, such that SHA256(SHA256(x)) is below a certain target (this is called mining). The first node to find a solution earns Bitcoins.

The Bitcoin network adjusts this target so that on average, a solution is found every 10 minutes, based on the total computational rate (MH/s) of the network.

A node's chance of winning is roughly equal to the fraction of total MH/s that it contributes to the network.

Mining requires the latest technology and/or low electricity costs to remain profitable over time. Only the most power-efficient survive.

In mid-2011, GPU mining was highly profitable, with many ATI GPUs paying for themselves in 6-9 months, counting power (but not cooling, maintenance, configuration, or other) costs. However, as an increasing number of GPU miners chased those returns, the difficulty adjusted and large-scale GPU mining inevitably became unprofitable.

Field Programmable Gate Array miners are under active development and use around 1/10th the power of a GPU, at the same performance level (MH/s). The upfront capital investment is higher than for GPUs; however, once made, the lower operational costs should enable FPGA miners to earn a significant monthly profit, even at price and difficulty levels where GPUs cannot. FPGAs are more power-efficient for mining, and over time are likely to make GPU mining unprofitable. Once the electricity to run a GPU costs more than the bitcoins it can produce, most miners will turn them off, and either sell their GPUs, or repurpose them.

A GPU process shrink does not change this situation; a 45nm FPGA still uses less electricity per MH than a 28nm GPU. And of course - 28nm FPGAs will arrive around the same time as 28nm GPUs, keeping FPGAs firmly ahead throughout 2012.

Now is the best time to switch to FPGA-based mining, to enjoy a major technological advantage over most other miners.

The FPGA End-Game

Large-scale miners who are willing to make the initial investment in FPGA mining should be able to mine a substantial portion of the remaining coins, with no operational threat from GPUs for at least the next 2 years. It looks likely that miners using GPUs will need to migrate to FPGAs to remain profitable during 2012.

Why not build an ASIC?

It's extremely expensive to build an ASIC that can outperform high-volume 40nm/28nm FPGAs. A 40nm mask set costs around $4M. Older technologies are less expensive, but above 130nm, probably cannot outperform a 28nm FPGA. At the current price and liquidity of Bitcoin, an ASIC would be an extremely risky investment. Most likely, the mining community will switch to FPGAs first and move to ASICs if/only if the Bitcoin ecosystem matures and expands considerably.

To Learn More..

Join #bitcoin-fpga on freenode. There's a small community of talented folks working on a variety of designs.


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