FPGA Mining:  Why cooling solutions matter

In 2018 mining farms have started observing that FPGAs are getting back in the game when we talk about mining.

Initially, the only solutions available on the market have been the Xilinx VCU 1525 (produced in low scale), followed by BCU 1525, produced instead on a medium scale.

In addition to these two types of FPGAs, many other manufacturers such as HUAWEI, INTEL and even XILINX have announced the release of a dedicated line.

In general, the FPGA boards have not been designed explicitly for mining, but if they get programmed properly, the same could reach a very high computing power on many algorithms.

Usually, the intensive and prolonged use of the board produces a heat that must be evaporated efficiently in order to secure good performance and longer-life of the board itself (duration and a performance over time).

Xilinx VCU 1525Xilinx BCU 1525Xilinx Alveo U200

Exactly for this reason, there are three different dissipation solutions that could be applicable today:

1. Air cooling solution
2. Water block solution
3. Immersion cooling solutionsAir Cooling Solution

Air Cooling Solution

In order to maximise and optimise the performance of the boards, many miners are coming up with different solutions that can also help with air cooling. Some well-known testers of the international community have developed and tested several mechanisms to improve the performance respectively. Here it is possible to find some of the tests.

Stock heatsink, axial fanModified heatsink and backplate, 3d flow embedding device, fanEconomy and not stable solutions. These are good solutions, but the changes to be made to the card and the performances that can be achieved are not very good, also you need to spend some money around 250–300$ for all the components (heatsink, backplate, 3d print part, fan).

The core and regulators temperature remain higher and is really dangerous for the board.

It could be an optimal solution for the miner that owns one or two FPGAs as it is not scalable.

Water Block Solution

Another system which is very appreciated by the miners is the so called Water Block (WB).

With the WB it is possible to keep the chip’s temperature very low (around 40 ° C) but the power regulators work at a limited temperature (from 80 to 90 ° C).

DimasTech Waterblock on BCU 1525DimasTech WaterBlock

Compared to the air cooling, the WB is clearly a better solution, having in mind the excellent performance that can be achieved with the card. Another positive point is that the WB method is also safer. However, from my point of view, we have only two limitations on the WB:

1 — a specifically designed WB model must be built for each board (technical time for its development)

2 — difficulty in assembling the hardware components, hence there is a potential risk of leakage in the system.

3 — High cost of the system — for one card it is approximately $ 300

Immersion Cooling Solution

For many reasons, the best in class solution seems to be the Immersion Cooling System.

With the immersion cooling, the temperature stability can be guaranteed on all parts of the board (core, regulator, pcb).

All in-one Immersion cooling solution

All in-one Immersion cooling solution

The main positive aspects are:

1- Easy installation;

2- Guaranteed benefits (core temperature and regulators are safe also with high OverClock);

3- Durability (Longer lifetime of the hardware);

4- The system is suitable for different types of cards;

The Immersion cooling system for 8 card costs around 4000 $.

Final Consideration

In order to use the air-cooled cards, persons are usually forced to make them work by decreasing the core voltage and frequency to maintain acceptable temperatures.

Due to the fact that the Immersion cooling is lowering the power consumption by 20–30%, the daily mining revenue is obviously higher.

With the use of the WB, it is possible to  achieve better results as well but the two complications (1. WB for each type of card and 2. risk of leakages/loss) cannot be ignored.

Based on all experiments and quality checks, maybe the best cooling solution is the immersion solution for the following reasons:

1- Compact and scalable;

2- 100% reliability and safety;

3- Possibility to re-use it for other cards or asics;

4- Optimal chip’s and regulators’ temperature;

5- Total control of the system remotely.