CPU mining is a process of adding transaction records to the public ledger of cryptocurrency by performing necessary calculations with a Central Processing Unit (CPU). A CPU is a part of computer that provides computing power for execution of operations performed by software installed on that computer.
Central Processing Units are designed in such a way that they are very suitable for rapid switching between different tasks. CPUs should be very well adjusted for beginning of a new type of work so a user shouldn’t wait much between working with various programs. CPU's are also highly capable of following instructions of the "if this, do that, otherwise do something else" type for fast execution of algorithms. However, the necessity of fast switching between tasks made CPUs not very well prepared for repetitive and long mathematical calculations. CPUs can do math, as inside every CPU is one or more "Arithmetic/Logic Units" (ALU's). However, GPU has much more ALUs than CPU and as a result, they can do large amounts of mathematical work in a greater quantity than CPU.
CPU mining was initially allowed in Bitcoin client’s earlier versions but pretty soon hashrate of the network grew too much for CPU mining to be profitable. The amount of produced Bitcoins became lower in value than a power needed to operate a CPU. As a useless feature, CPU mining was removed from Bitcoins core, GPU mining became the only way to mine Bitcoins for some time. Most of other cryptocurrencies, especially popular ones, also can’t be profitably mined with CPU due to high hashrate of the network. However, it is possible to find a new promising crypto that can be successfully mined with CPU and gather some profit in a long term.
There are some cryptocurrencies, especially designed for profitable mining with CPU. Most of CPU mining coins are CryptoNight-based coins like Bytecoin, Quazarcoin, Monero, Electroneum and some others. CryptoNight cryptocurrencies are developed based on ideas of CryptoNote team, one of which is making mining available for everyone despite their differences in computing equipment. As CryptoNight-based coins use CryptoNote’s egalitarian Proof-Of-Work, they are utilizing built-in CPU instructions, which are very hard and too expensive to implement in special purpose devices (ASICs), but perfectly suitable for ordinary PCs.
Due to mentioned approach, Bytecoin and its forks were only CPU-minable and ASIC-resistant. However, some of the current ASICs work perfectly fine with multiple CryptoNight coins and CPU mining of them isn’t that profitable anymore. Still, Monero team, for example, is actively fighting ASIC participation in mining of the cryptocurrency and even made a hard fork to let Monero CPU mining remain the only way to make new XMR coins. There are also come cryptocurrencies that are not CryptoNight-based and initially allowed profitable CPU mining, some of them are Litecoin, Dash, Hatch and ZCash.
Pros & Cons
- CPU mining is available for everyone who has a computer
- Some cryptocurrencies are only CPU-minable
- CPU mining is a good way to try cryptocurrency mining out before making any purchases and investments
- Using CPU as addition to GPU mining can lead to some additional benefit for a miner
- CPU mining is unprofitable to use for the mining of most cryptocurrencies
- CPU mining is not allowed for mining of some cryptocurrencies
Profitability of CPU mining can be relatively high in three cases.
- Proof-of-Work cryptocurrency that is mined is not strongly demanding on computing power of miner’s equipment due to its being newly established and/or having low hashrate.
- Mined cryptocurrency is specifically designed for CPU-mining and restricts more productive types of mining hardware from participation in transaction validation.
- Miner has an access to many CPUs or CPU mining rig and a source of cheap or even free electricity.
In most of other cases CPU mining is not profitable anymore for absolute majority of cryptocurrencies.
Some coins that can be mined with CPUs: