ASIC

An ASIC (application-specific integrated circuit) is hardware built to do exactly one job. A mining ASIC computes one algorithm, such as SHA-256 or Scrypt, orders of magnitude faster and more efficiently than any general-purpose CPU or GPU.

The first Bitcoin ASIC miners shipped in early 2013. Within a short time they made CPU and GPU mining of Bitcoin pointless, because one machine did the work of hundreds of graphics cards for far less power. The same has since happened to several other algorithms.

ASICs are usually rated by hashrate and by efficiency. Efficiency is the energy used per unit of work, often given in joules per terahash for SHA-256. Lower is better. Two machines with the same hashrate can have very different power bills, so efficiency often decides whether a machine is profitable.

The trade-off is inflexibility. An ASIC mines only its algorithm and is scrap for everything else. If its coin's difficulty rises, its price falls or a newer model arrives, the machine cannot switch to another job. ASICs are also loud and hot, which makes most of them unsuited to a home or an office.

Some algorithms are designed to resist ASICs. They rely on large amounts of memory or on random code that a general processor handles well, so custom chips gain little. RandomX, used by Monero, is built for ordinary CPUs. Ethash, the old Ethereum algorithm, leaned on memory for the same reason, though ASICs for it did eventually appear.

A common mistake is to buy an ASIC from its hashrate alone. Check its efficiency, your electricity price, the noise, the warranty and the coins its algorithm can mine. A used machine may be cheap because its efficiency no longer pays at current difficulty.

To mine with an ASIC, open its web interface, enter the pool's host and port, your wallet address as the login and a worker name. The pool's How to Mine page shows the values for your region.