ASIC: The Specialized Chip behind Bitcoin Mining

An ASIC (application-specific integrated circuit) is a chip that is designed for one task instead of general computing. In Bitcoin mining, an ASIC chip computes Bitcoin’s SHA-256 hashes much faster, and with much less energy per hash, than a general-purpose processor. An ASIC miner, or Bitcoin ASIC, is the machine built around many of these chips.

An ASIC miner’s speed is rated in terahashes per second (TH/s), and one terahash is a trillion hashes. The machine’s efficiency is rated in joules per terahash (J/TH), which is the energy the machine spends on each trillion hashes.

What Does an ASIC Chip Do in Bitcoin Mining?

Bitcoin’s proof of work asks miners to hash a candidate block header. A candidate block header is the 80-byte summary of a block that a miner is trying to add to the chain. The header holds a reference to the previous block, a fingerprint of the block’s transactions, the time, the target, and a 32-bit number called the nonce.

To hash the header, a miner runs it through the SHA-256 hash function twice. A hash is the fixed-length result that a hash function produces from its input. Bitcoin reads that result as a number, and a block is valid only if the number is at or below the target that the network sets.

When a hash misses the target, the miner changes the nonce and hashes the header again. Each hash is one guess at a valid block.

An ASIC chip for Bitcoin mining has circuits customized for that one calculation, double SHA-256. A general-purpose processor is designed to run any program, while an ASIC chip does one job, which is why it computes far more hashes per second and spends far less energy on each hash. The ASIC chip largely sets a machine’s cost and efficiency, and it is usually the part that draws the most power.

A Bitcoin mining machine carries many ASIC chips on circuit boards called hashboards. The combined output of those chips is the machine’s hashrate, which is the number of hashes the machine computes per second.

Why Did Bitcoin Mining Move from CPUs and GPUs to ASICs?

In Bitcoin’s early years, the standard client software let users mine BTC with a computer’s CPU (central processing unit). A CPU is the general-purpose processor that runs a computer’s programs.

From 2010, Bitcoin mining moved to GPUs (graphics processing units). A GPU is the processor on a graphics card. By mid-2011, FPGAs (field-programmable gate arrays) had become popular as well. An FPGA is a chip that can be configured after manufacturing to carry out a chosen logic function.

The first ASICs designed for Bitcoin mining were released in 2013. ASICs outperform CPUs, GPUs, and FPGAs in both speed and energy per hash.

The Bitcoin Wiki, a community-maintained reference on Bitcoin, collects benchmarks for hardware of the 2010-2013 era. Two desktop CPUs of that era, the Intel Core 2 Quad Q6600 and the Core i5-750, computed about 11 and 14 MH/s (million hashes per second).

The Antminer S21 XP is a current ASIC miner made by the manufacturer Bitmain, which lists it at 270 TH/s as of October 2026. That rate equals 270 million MH/s. Measured that way, the S21 XP is roughly 330,000 times as fast as the AMD Radeon HD 7970, a high-end graphics card of the early 2010s that the Bitcoin Wiki benchmarks put at about 825 MH/s.

A graphics card can still compute SHA-256, but GPU Bitcoin mining no longer competes with ASIC Bitcoin mining. The Bitcoin Wiki says that GPU mining of Bitcoin “has become impracticable” because the network’s total hashrate rose so far after ASICs arrived.

What Is Inside an ASIC Bitcoin Miner?

A Bitcoin mining machine today is an ASIC miner, also called an ASIC bitcoin miner or, in everyday usage, a Bitcoin mining rig. An ASIC miner combines four kinds of parts: hashboards, a control board, a power supply, and a cooling system.

In a teardown of Bitmain’s Antminer S19j Pro, Hashrate Index, a Bitcoin mining data publisher, counted three hashboards with 126 chips each, or 378 chips in total. The same review notes that most ASIC miners use three hashboards.

The control board is the machine’s small built-in computer. The control board runs the firmware, which is the software that operates the machine. The control board also coordinates the hashboards and reads the sensors.

Over Ethernet, the control board connects an ASIC miner to a mining pool. A mining pool is a group of miners who combine their hashing work and share the block rewards they win in proportion to the work each one contributed.

The power supply converts alternating current (AC) from the mains into the low-voltage direct current (DC) that the chips run on. In the S19j Pro, the power supply turns 200-277 V AC into 12-15 V DC. For the Antminer S21 XP, as of October 2026, Bitmain specifies an input of 220-277 V AC at 20 A and a power supply output of 4,000 W, which is more than the machine’s typical draw of 3,645 W. Bitmain lists the S21 XP’s power supply as a separate model.

Air-cooled ASIC miners use fans to carry heat out of the case. The S19j Pro has four fans, two that pull air in and two that push it out.

Hydro ASIC miners replace air cooling with water or another liquid coolant that flows through the machine. Immersion Bitcoin mining submerges the ASIC miner in a non-conductive (dielectric) fluid. The fluid carries heat away far better than air and doesn’t conduct electricity, so it can surround the boards and remove their heat without air blown over heatsinks.

How Do You Read an ASIC Miner’s Spec Sheet?

As of October 2026, Bitmain’s specification page for the Antminer S21 XP, an air-cooled ASIC miner, lists these typical values:

• Hashrate: 270 TH/s, plus or minus 3%
• Power: 3,645 W at the wall, plus or minus 5%, measured with 25 °C inlet air
• Efficiency: 13.5 J/TH, plus or minus 5%
• Algorithm: SHA-256, for BTC and two other SHA-256 coins
• Noise: 76 dBA (A-weighted decibels) at maximum fan speed

Hashrate is an ASIC miner’s speed, much like the horsepower of a car engine. Power is the electricity the machine draws while it runs. Efficiency links the two and works like a car’s fuel consumption, so a lower J/TH figure means the machine spends less energy on the same work.

You can check the efficiency line by dividing power by hashrate. For the S21 XP, 3,645 W divided by 270 TH/s equals 13.5 watts per TH/s (W/TH). W/TH and J/TH give the same number because one watt is one joule per second.

Spec-sheet figures are typical values, not promises. Bitmain measures the S21 XP with 25 °C inlet air and allows a spread of 3% on hashrate and 5% on power and efficiency, so a machine running in hotter air may not match the sheet.

A digital bitcoin miner from GoMining is backed by real mining power from ASIC machines in GoMining’s data centers. Each digital bitcoin miner has its mining power stated in TH and its energy efficiency stated in W/TH, the same measure as the J/TH line on an ASIC spec sheet. Electricity is part of the maintenance fee deducted daily from a digital miner’s BTC rewards, and a lower W/TH means a lower electricity charge within that fee.

What Are the Limits of an ASIC Miner?

An ASIC miner runs one hashing algorithm and nothing else. A SHA-256 machine such as the S21 XP can mine BTC and the other SHA-256 coins that Bitmain lists on its spec sheet, but the machine cannot mine coins that use a different algorithm.

Older ASIC miners lose ground as newer generations lower J/TH. As of October 2026, Bitmain lists the S19 XP, an earlier generation, at 141 TH/s, 3,031.5 W, and 21.5 J/TH. Against the S21 XP’s 13.5 J/TH, the S19 XP uses about 59% more power for each TH/s of hashrate, so the older machine spends more electricity on the same work.

An air-cooled ASIC miner is loud and runs hot. Nearly all the electricity a Bitcoin mining machine draws ends up as heat. As of October 2026, Bitmain rates the S21 XP at 3,645 W, so the machine gives off nearly that much heat for as long as it runs.

The National Institute on Deafness and Other Communication Disorders (NIDCD), part of the US National Institutes of Health, puts normal conversation at about 60-70 dBA. The NIDCD says that sounds at or below 70 dBA are unlikely to cause hearing loss even after long exposure, and that long or repeated exposure at or above 85 dBA can cause it. The S21 XP’s 76 dBA is louder than normal conversation and falls between those two levels. Bitmain does not state the distance at which it measured that figure, so the comparison is approximate.

In a report based on survey data from mid-2024, the Cambridge Centre for Alternative Finance, a research center, found that the largest manufacturer held about 82% of the market for SHA-256 ASIC miners. The same report gave the top three manufacturers more than 99% of that market. That concentration means the supply of new Bitcoin mining machines depends on a few makers.