Why are fewer and fewer people using CPU/GPU for mining? What are the advantages of ASIC mining machines?

In the seventh season of Game of Thrones, the White Walkers have turned everyone outside the Northern Wall into zombies and successfully chiseled a large gap in the thick wall. Winter is coming! In the cryptocurrency circle, a war is also brewing. After successfully destroying Bitcoin, Bitmain began to sell its Antminer E3 cryptocurrency mining machine specially developed for Ethereum mining. This made the Ethereum community very nervous, and a proposal has been submitted to change the mining algorithm, with the ultimate goal of making Ethash ASIC miners incompatible with the network. Why are they doing this?

Bitmain is the world's largest mining machine manufacturer. The ASIC mining machines it produces have mastered more than 60% of the Bitcoin network's computing power, and are known as the mining tyrants, which has seriously affected the basic characteristic of Bitcoin's decentralization and successfully led to Bitcoin's hard fork. Most people in Ethereum hope to transfer the consensus algorithm of cryptocurrency from PoW to PoS, which means that heroes are not judged by computing power, avoiding repeating Bitcoin's mistakes.

The injured are not just Ethereum, but AMD and Nvidia. Bitmain, a young company founded in 2013, had an operating profit of $3 billion to $4 billion in 2017, while Nvidia's operating profit was $3 billion during the same period! It is like an invisible boss. Bitmain's high profits come from the fact that its mining machines have completely driven out GPUs and even FPGAs in the Bitcoin field based on the SHA algorithm. GPU mining has retreated to the Ethash algorithm field such as Ethereum. If ASIC mining machines invade this field again, it will have a great impact on GPU manufacturers AMD and Nvidia (although the two major GPU manufacturers refuse to disclose the proportion of mining graphics cards), and they may be completely expelled from the mining industry!

Putting aside these business stories, if we look back at the development of mining machines over the years, we will find a clear path:

CPU->GPU->FPGA->ASIC

Today we will discuss the driving factor of this main line development from the perspective of hardware technology: computing power per watt. We will also give some data at the end.

Hashrate per Watt

To discuss why the computing power per watt is different between CPU, GPU and ASIC, we must first clarify why chips need to consume electricity and what it is related to.

We simply view the integrated circuit as a collection of field effect transistors FET. With each flip, these many FETs consume energy. A simple schematic diagram of a FET is as follows:

Figure 1

When the input is low, CL is charged, and we assume that a joule of energy is stored in the capacitor. When the input becomes high, this energy is released, and a joule of energy is released. Because CL is very small, this a is also very small and can be almost ignored. But if we flip this FET at a frequency of 1GHz, the energy consumption is a × 10^9, which cannot be ignored. In addition, there are billions of FETs in the CPU, and the energy consumed becomes considerable.

From this we can see that the energy consumption of the CPU is related to how many transistors are involved in the work , and is positively correlated with the frequency. The execution of an instruction in the CPU, whether to schedule the arithmetic unit, whether to access external memory, whether to write back, whether in L1 or not, will all make a difference in the number of transistors mobilized. In summary, the power consumption pie chart of each stage in the pipeline is as follows:

It can be seen that Fetch instructions and decode occupy the majority, while our execution only occupies %9 !! This is also the reason why ASIC is very power-saving while CPU is very power-consuming to achieve the same function:

ASIC does not need other operations, just focus on calculating HASH! It can only do one thing, focus on one thing, and save the most money. This is the advantage of ASIC.

data

The concept of computing power per watt is relatively abstract. In fact, we often measure it by hash per watt. Let's compare the data of CPU, GPU, FPGA and ASIC in mining efficiency and economy:

For the sake of fairness and ease of calculation, the four selected mining equipment are all 184 US dollars (green box). From the perspective of hash per watt, GPU is 1800 times that of CPU; ASIC is 188 times that of GPU and 340,000 times that of CPU!

We can also see from the blue part of the picture that currently the only machine that can make money in Bitcoin mining is ASIC mining machine . GPU/CPU is losing more and more money the more it mines, and it is not enough to cover the electricity bill! (The amount of Bitcoin produced each year is fixed, and the 340,000 times efficiency will of course mine faster). So those who still want to use CPU to mine Bitcoin should forget it.

in conclusion

The E3 mining machine is not expensive:

The performance of this generation is only 6 times that of 1080Ti, which is 180 Megahash. But this is just the first step, and the following products are very scary. No wonder the Ethereum community is so nervous and wants to go to war with ASIC mining machines.

For the average spectator, this might be a good thing. If GPUs are completely driven out of the mining industry, the price of GPUs will not be driven up to the sky.