Application-Specific Integrated Circuits are dramatically faster and more efficient at their one task than general-purpose CPUs or GPUs. Where a mature ASIC market exists, as for Bitcoin's SHA-256 or Litecoin's Scrypt, other hardware is not economically competitive.
The trade-off is inflexibility: an ASIC built for SHA-256 can only ever mine SHA-256 chains. If that coin becomes unprofitable, the machine has no alternative use and its resale value falls with it.
This definition is educational and not financial advice. Crypto is volatile and high-risk — always do your own research.
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