FPGA Crypto Mining: Which Miners to Use and Are They Better

Published: 9th December, 2023 | Last Updated: 19th April, 2024

Hudson Kisia

Hudson Kisia has been researching and writing content for ElementalCrypto since 2022. He has been writing about crypto, blockchains, and mining for more than 5 years now.

In this post I will tell you all you need to know about FPGA crypto mining.

Cryptocurrency mining operation is a complex endeavor that requires careful selection of an appropriate mining rig.

During the early stages of Bitcoin mining, miners competed for the best CPUs in the market (see What is Bitcoin for more).

However, as the network difficulty increased, CPU mining became unprofitable. This quickly paved the way for GPU mining where video graphics cards became the primary hardware for GPU miners. 

From GPU to FPGA

FPGA architecture
A simple FPGA architecture

Eventually, Bitcoin’s network difficulty outgrew the processing power of GPU miners. Thus, an alternative solution had to be found. This ushered the use of Field-Programmable Gate Array (FPGA). Being programmable, FPGA could adapt to the expanding volume of crypto coins, each requiring a different algorithm. The flexibility and scalability of Field-Programmable Gate Arrays gave rise to cryptocurrency mining farms.

From FPGA to ASIC

As Bitcoin mining became more lucrative, specialization became viable and profitable.  Application-Specific Integrated Circuit (ASIC) was created to meet this specialization requirement. Thus, Bitcoin could have an ASIC miner that catered only to Bitcoin’s SHA-256 Algorithm. Unlike an FPGA miner, ASIC miners don’t require a complicated setup to run.  This made ASIC mining a popular option for Bitcoin. Yet, FPGA is still widely used. Why? Let’s explore some of the reasons. But, before then, let’s explore the best FPGAs for passive crypto mining.

The best FPGAs for crypto mining

While there are many FPGA brands in the market, just a few of them have dominated the cryptocurrency mining domain. The following are the leading lights:

1. Ultraminer FPGA

Ultraminer FPGA board
Ultraminer FPGA board

Promoted by Crowd Supply, Ultraminer FPGA, is an open project financed by the community through crowdfunding. This FPGA miner utilizes the Xilinx Kintex UltraScale+ KU3P. It is not only loved by novice miners but is also commonly used as a university project to enable students to understand how FPGA mining works. Besides, it is a very powerful yet affordable FPGA prebuilt mining rig.

2. Blackminer FPGA

BlackMiner F1 FPGA crypto mining rig
BlackMiner F1 crypto-mining rig

The following two major brands of Blackminer FPGA are popular with FPGA miners:

  • Blackminer F1
  • Blackminer F2

Of the Blackminer F series, F1 takes a sizeable chunk of popularity.

2. Xilinx FPGAs

Xilinx Zynq FPGA chip
Xilinx Zynq FPGA chip

Under the AMD flagship, Xilinx FPGAs include Xilinx Zynq, Xilinx UltraScale, Virtex UltraScale, and Kintex UltraScale.

3. Altera FPGAs

Altera's Cyclone V FPGA crypto mining board
Altera’s Cyclone V FPGA board

Under the Intel flagship, Altera devices include the Cyclone V series, Stratix series, Agilex series, Arria series, and MAX series.

Why FPGA?

Several factors make FPGAs ideal for mining cryptocurrencies. The following are some of these key factors:

1. Profitable

The overriding reason as to why FPGA is still used in the crypto-mining industry is that it is still profitable. It is far more profitable than GPU miners. Many home-based mining rigs still use FPGAs.

Yet, not all coins can be mined profitably using FPGA. For example, it is no longer profitable to mine Bitcoin using FPGA. Nonetheless, it is profitable to mine a hundred plus other coins using FPGA.

2. Programmable

A small-scale mining operation would require a mining rig that is capable of handling different algorithms to increase the chances of reaping mining rewards.

Unlike ASIC miners, FPGA can be programmed to suit many different mining algorithms. This means that the same FPGA miner can be used to mine different alt coins. It just takes a fraction of a second to switch from one FGPA’s configuration file to another.

3. Flexible

Since FPGA has multiple programmable blocks, you can configure a set of blocks to mine one type of coin while the other block mines another type of coin. As such you can use different mining algorithms on the same FPGA miner to mine different cryptocurrencies.  You can also program an FPGA block to mine different cryptocurrencies at different intervals.

4. Scalable

Many crypto mining farms, especially those that prefer to diversify their operations by mining different cryptocurrencies, find the use of FPGA hardware as the most optimal choice.

5. Versatile

FPGA can be programmed to suit different algorithms for different cryptocurrencies. This makes FPGA crypto miners highly adaptable to meet different needs at the same time.

6. Affordable

Compared to ASIC miners, an FPGA device is highly affordable.

Why not FPGA alternatives?

The choice of FPGA crypto mining should be based on the evaluation of its alternatives – GPU mining and ASIC mining. Why would one choose FPGA over GPU and ASIC miners?

1. FPGA vs GPU

Compared to graphics cards, FPGA cards have several advantages and disadvantages.

(a) Pros

The following are the main advantages of FPGA over GPU:

  • Highly customizable – FPGA can be programmed to cater to specific mining algorithms. GPU is not reprogrammable and may not do well in a highly specialized process such as the crypto mining process.
  • Highly scalable – FPGA device can easily scale compared to a GPU mining rig since it is easier to integrate various FPGA cards to operate as one coherent unit on an FPGA board.
  • Cost-effective – while the price of an FPGA device can be higher than that of a GPU device, in terms of cost per hash, FPGA cards tend to be cheaper than graphics cards.
  • Lower latency – FPGA has lower latency due to specific programming features that avoid delays caused by running redundant protocols.
  • Higher power efficiency – GPUs were not specifically designed for crypto mining. Thus, they have high redundancies that cost electricity. Even though FPGAs are also not specifically designed for crypto mining, they can be reprogrammed to avoid most of these redundancies. This results in higher energy efficiency and thus less power consumption.

(b) Cons

The following are the disadvantages of FPGA over GPU:

  • Requires customized FPGA software to run them – GPUs are generally plug-and-play devices. Apart from the Operating System, they don’t require a customized piece of software to run. On the other hand, you have to create custom software to run an FPGA hardware device.
  • Requires specialized skill – FPGAs have to be programmed to execute specialized functions. This requires specialized skills in hardware description languages, which may not be easy to find. GPUs are already programmed at the factory level.

FPGA vs ASIC

A typical Bitcoin miner is an ASIC device.  FPGA can also be used to mine bitcoins, but it is not profitable. However, there are many profitable coins where FPGA crypto mining does better than ASIC mining.  

(a) Pros

 Compared to ASIC, FPGA has the following advantages:

  • Reusable – Unlike ASIC miners which can only be used for a specific algorithm, FPGA crypto miners can be reused for other algorithms. For example, if you bought an ASIC miner for Bitcoin mining, if it turns out unprofitable, you cannot reuse the ASIC to mine other coins. However, you can reuse FPGA to mine other coins since it is just a matter of replacing the old configuration file with a new configuration file.
  • Flexible – Flexibility is what makes FPGA beat ASIC. We’ve already seen how flexible the FPGA miner is.
  • Lower risk of obsolescence – If you bought an ASIC miner to mine a certain type of cryptocurrency and that cryptocurrency ceases to exist, the ASIC miner becomes obsolete. However, for an FPGA crypto miner, all you need is to replace the configuration file with one that is configured to mine your new type of coin.

(b) Cons

Compared to ASIC, FPGA has the following disadvantages:

  • Lower computing efficiency – since FPGA cards are multipurpose, their circuits are not optimized for a certain specific algorithm. Thus, they are less efficient compared to ASIC miners whose specific task is to execute a predetermined algorithm.
  • Lower power efficiency – lower computing efficiency translates to lower power efficiency since some computing power is wasted. This translates into higher electricity costs.
  • Less compact design – FPGA boards have a larger form factor compared to ASIC boards. This is because FPGA boards have to incorporate components required for general-purpose usage. Furthermore, scalable FPGA boards need to have space for slots where pluggable FPGA cards can be inserted.
  • Less scalable – if you want to scale up crypto mining operations based on one mining algorithm (for example, Bitcoin mining only), then ASIC will be more scalable than FPGA. Furthermore, the relatively lower mining power of an FPGA means that you will require more FPGA cards and boards just to achieve the same level of scaling that an additional ASIC miner would achieve.

FPGA infrastructure

Setting up an FPGA crypto-mining infrastructure requires a combination of various pieces of hardware and software. The following are the most important:

1. Hardware

The FPGA hardware comprises the following main parts:

(a) FPGA boards

Like personal computers that have a motherboard, FPGA mining rigs have FPGA boards. The FPGA board can be designed to have several slots to handle multiple FPGA cards. They can be designed to have various USB ports to handle different peripheral devices and interconnections. You can easily find a ready-made FPGA development board in the market if you want to assemble your own FPGA mining rig.

(b) FPGA cards

Just as video graphics cards have a GPU embedded in them, FPGA cards have an FPGA chip embedded in them. This makes them easy to handle and insert into the FPGA boards.

(c) Flash memory

Since the bulk of the FPGA firmware isn’t embedded in the ROM, it has to reside in an alternative memory. Flash memory is the best alternative as it is the closest to the RAM in terms of access and loading speed. RAM is temporary and thus the memory gets erased when power is switched off. The other alternative would be a storage disk (Hard disk or SSD), but storage disks are extremely slow in terms of access and loading speeds which will extremely slow down the crypto mining process.

(d) Power Supply Unit

Most FPGA boards don’t come with an integrated power supply unit, except for those with less powerful FPGA chips. If you have to assemble your FPGA mining rig, you will need to buy it separately.

Furthermore, you need to build a power supply system that has a voltage regulator and backup to guarantee the continuity of the crypto-mining process in case of a power outage. Unlike GPUs that have their firmware embedded in ROM, FPGAs have their firmware in temporary memory and thus the entire memory gets erased during a power outage. The firmware has to be reloaded afresh from the flash memory for the FPGA to run again – a very slow and tedious process.

(e) Cooling system

FPGA chips can easily overheat when put to high-intensity work such as the crypto mining process. Thus, to protect the chips from being damaged by heat, and also to ensure maximum performance, a proper cooling system needs to be put in place. Each FPGA chip has specific cooling system requirements that you need to implement.

2. FPGA Software

Several open-source free software exist that can be used for FPGA crypto mining. Verilog program is the most widely used Hardware Description Language (HDL) for FPGA programming. HDL is a special type of programming language used to describe and command logical operations in digital circuits such as those of FPGA.

RTL Verilog is a special subset of the Verilog program that is responsible for RTL programming. RTL stands for Register-Transfer-Level. As the name suggests this special program whose specific purpose is to manage inter-register transfers within the FPGA memory.

3. FPGA Setup

Once you have the hardware and software in place, the next task is FPGA setup. In this setup, the first step is to assemble the mining hardware. You can bypass this step by acquiring one of the ready-made FPGA mining rigs we highlighted above. Once the hardware is assembled the next step is to carry out FPGA configuration. This will require you to create a configuration file. After creating the configuration file, you can then load it into the flash memory and test the FPGA miner to ensure it works well before launching your first crypto-mining project. Consistently fine-tune the FGPA miner to weed out unexpected behavior and thus ensure the best performance.

FPGA crypto mining enterprise

Like any other business, the profit motive is the primary objective of an FPGA crypto-mining enterprise.

To successfully carry out this enterprise, you need to factor in the following key elements:

1. FPGA mining coins

As a rule of thumb, all those coins that do not require the use of ASIC miners can be mined by FPGA crypto mining rigs. Similarly, all those coins that can be mined by CPUs and GPUs can also be mined by an FPGA crypto mining rig.

However, as a matter of policy, some coins have an algorithm that automatically blocks the use of high hash rates. While you can use FPGAs with low hash rates, it may be uneconomical to buy them when a simple Raspberry Pi rig can profitably do the same mining work at a small fraction of the price.

The following are some of the popular coins that can be profitably mined using FPGA:

  • Monero – uses CryptoNightV7 algorithm
  • MaxCoin – uses the Keccak algorithm
  • Gentarium – uses the Lyra2z algorithm
  • Denarius – uses the Tribus algorithm
  • Zen Protocol – uses the Keccak-ZP algorithm
  • oxBitcoin – uses the 0xToken algorithm
  • Nexus – uses the Nexus algorithm

2. FPGA mining rewards

Each blockchain has its block reward. You can use the FPGA mining calculator to determine how much FPGA crypto mining rewards you are potentially going to gain from a given FPGA miner.

Almost every FPGA mining pool has a mining calculator. Nonetheless, the following are the most common FPGA mining calculators:

3. FPGA costs

Apart from the capital cost of acquiring an FPGA crypto mining device, the running cost is extremely important. Among these running costs, the cost of electricity is the most significant. Thus, power usage is an important consideration in determining whether the mining enterprise will be profitable or not.

4. FPGA profitability

While mining rewards are a strong indicator of profitability, other factors come into play that may not be captured by the FPGA mining calculators. These include;

  • Rental cost – mining rigs take up space and that space takes up rent.
  • FPGA setup cost – the cost of assembling, programming, and configuring the FPGA mining rig isn’t cheap.
  • Management cost – the cost of running your crypto-mining operation
  • Capital cost – the cost of buying the FPGA equipment
  • Opportunity cost – the cost of the next best opportunity sacrificed. For example, you sacrifice interest-earning on capital when you decide to invest in FPGA mining equipment. You sacrifice several hours of wage when you choose to spend those labor hours on setting up your FPGA mining equipment. You sacrifice other potential uses of that space that you allocate to your mining rig. There are many more opportunity costs that you should consider.

What FPGA mining calculators will reflect are gross profit, but not net profit. As a business entrepreneur, you need to consider the net profit.

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Hudson Kisia has been researching and writing content for ElementalCrypto since 2022. He has been writing about crypto, blockchains, and mining for more than 5 years now.

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