In this article by Albert Szmigielski, author of the book Bitcoin Essentials, we will take a look at mining with Field-Programmable Gate Arrays, or FPGAs. These are microprocessors that can be programmed for a specific purpose. In the case of bitcoin mining, they are configured to perform the SHA-256 hash function, which is used to mine bitcoins. FPGAs have a slight advantage over GPUs for mining. The period of FPGA mining of bitcoins was rather short (just under a year), as faster machines became available. The advent of ASIC technology for bitcoin mining compelled a lot of miners to make the move from FPGAs to ASICs. Nevertheless, FPGA mining is worth learning about.
We will look at the following:
- Pros and cons of FPGA mining
- FPGA versus other hardware mining
- Best practices when mining with FPGAs
- Discussion of profitability
(For more resources related to this topic, see here.)
Pros and cons of FPGA mining
Mining with an FPGA has its advantages and disadvantages. Let’s examine these in order to better understand if and when it is appropriate to use FPGAs to mine bitcoins. As you may recall, mining started on CPUs, moved over to GPUs, and then people discovered that FPGAs could be used for mining as well.
Pros of FPGA mining
FPGA mining is the third step in mining hardware evolution. They are faster and more efficient than GPUs.
In brief, mining bitcoins with FPGAs has the following advantages:
- FPGAs are faster than GPUs and CPUs
- FPGAs are more electricity-efficient per unit of hashing than CPUs or GPUs
Cons of FPGA mining
FPGAs are rather difficult to source and program. They are not usually sold in stores open to the public. We have not touched upon programming FPGAs to mine bitcoins as it is assumed that the reader has already acquired preprogrammed FPGAs. There are several good resources regarding FPGA programming on the Internet. Electricity costs are also an issue with FPGAs, although not as big as with GPUs.
To summarize, mining bitcoins with FPGAs has the following disadvantages:
- Electricity costs
- Hardware costs
- Fierce competition with other miners
Best practices when mining with FPGAs
Let’s look at the recommended things to do when mining with FPGAs. Mining is fun, and it could also be profitable if several factors are taken into account.
Make sure that all your FPGAs have adequate cooling. Additional fans beyond what is provided by the manufacturer are always a good idea. Remove dust frequently, as a buildup of dust might have a detrimental effect on cooling efficiency, and therefore, mining speed.
For your particular mining machine, look up all the optimization tweaks online in order to get all the hashing power possible out of the device.
When setting up a mining operation for profit, keep in mind that electricity costs will be a large percentage of your overall costs. Seek a location with the lowest electricity rates. Think about cooling costs—perhaps it would be most beneficial to mine somewhere where the climate is cooler.
When purchasing FPGAs, make sure you calculate hashes per dollar of hardware costs, and also hashes per unit of electricity used. In mining, electricity has the biggest cost after hardware, and electricity will exceed the cost of the hardware over time. Keep in mind that hardware costs fall over time, so purchasing your equipment in stages rather than all at once may be desirable.
To summarize, keep in mind these factors when mining with FPGAs:
- Adequate cooling
- Optimization
- Electricity costs
- Hardware cost per MH/s
Benchmarks of mining speeds with different FPGAs
As we have mentioned before, the Bitcoin network hash rate is really high now. Mining even with FPGAs does not guarantee profits. This is due to the fact that during the mining process, you are competing with other miners to try to solve a block. If those other miners are running a larger percentage of the total mining power, you will be at a disadvantage, as they are more likely to solve a block.
To compare the mining speed of a few FPGAs, look at the following table:
|
FPGA |
Mining speed (MH/s) |
Power used (Watts) |
|
Bitcoin Dominator X5000 |
100 |
6.8 |
|
Icarus |
380 |
19.2 |
|
Lancelot |
400 |
26 |
|
ModMiner Quad |
800 |
40 |
|
Butterflylabs Mini Rig |
25,200 |
1250 |
FPGA versus GPU and CPU mining
FPGAs hash much faster than any other hardware. The fastest in our list reaches 25,000 MH/s. FPGAs are faster at performing hashing calculations than both CPUs and GPUs. They are also more efficient with respect to the use of electricity per hashing unit. The increase in hashing speed in FPGAs is a significant improvement over GPUs and even more so over CPUs.
The profitability of FPGA mining
In calculating your potential profit, keep in mind the following factors:
- The cost of your FPGAs
- Electricity costs to run the hardware
- Cooling costs—FPGAs generate a decent amount of heat
- Your percentage of the total network hashing power
To calculate the expected rewards from mining, we can do the following: First, calculate what percentage of total hashing power you command. To look up the network mining speed, execute the getmininginfo command in the console of the Bitcoin Core wallet. We will do our calculations with an FPGA that can hash at 1 GH/s. If the Bitcoin network hashes at 400,000 TH/s, then our proportion of the hashing power is 0.001/400 000 = 0.0000000025 of the total mining power.
A bitcoin block is found, on average, every 10 minutes, which makes six per hour and 144 for a 24-hour period. The current reward per block is 25 BTC; therefore, in a day, we have 144 * 25 = 3600 BTC mined.
If we command a certain percentage of the mining power, then on average we should earn that proportion of newly minted bitcoins.
Multiplying our portion of the hashing power by the number of bitcoins mined daily, we arrive at the following:
0.0000000025 * 3600 BTC = 0.000009 BTC
As one can see, this is roughly $0.0025 USD for a 24-hour period.
For up-to-date profitability information, you can look at https://www.multipool.us/, which publishes the average profitability per gigahash of mining power.
Summary
In this article, we explored FPGA mining. We examined the advantages and disadvantages of mining with FPGAs. It would serve any miner well to ponder them over when deciding to start mining or when thinking about improving current mining operations. We touched upon some best practices that we recommend keeping in mind.
We also investigated the profitability of mining, given current conditions. A simple way of calculating your average earnings was also presented. We concluded that mining competition is fierce; therefore, any improvements you can make will serve you well.
Resources for Article:
Further resources on this subject:
- Bitcoins – Pools and Mining [article]
- Protecting Your Bitcoins [article]
- E-commerce with MEAN [article]