ASICs, or application-specific integrated circuits, are hardware designed to do one thing and one thing only. That one thing varies from ASIC to ASIC, but for Bitcoin, it is to mine Bitcoin.
More specifically, to mine SHA-256 hashes very quickly.
ASICs were first used for Bitcoin in 2013 when the first batch of ASICs designed specifically for Bitcoin mining were released by Butterfly Labs. Since then, ASICs have become more and more common in the Bitcoin mining world.
In fact, according to BitFury CEO Valery Vavilov, about 85% of Bitcoin mining is done with ASICs.
So do you need an ASIC to mine Ethereum? The short answer is no. The long answer is a bit more complicated.
Ethereum uses a different hashing algorithm than Bitcoin. Ethereum’s hashing algorithm is called Ethash and it’s a memory-hard hashing algorithm.
That means that in order to be effective at mining Ethereum you need a lot of RAM. And that’s something that ASICs are not very good at.
ASICs are very good at doing one thing and one thing only. That might be fine for Bitcoin where all you need is a fast SHA-256 miner, but it’s not so great for Ethereum where you need a lot of RAM as well.
So while you don’t need an ASIC to mine Ethereum, an ASIC would not be very effective at mining Ethereum. If you want to mine Ethereum effectively, you’re better off with a GPU or a CPU.