It used to be that litecoin mining could only be done by GPU, but now ASIC machines are getting all the glory.
For a time, new miners preferred to mine litecoin instead of bitcoin because ASIC miners had rendered old-fashioned GPU mining for Bitcoin unprofitable. During that time, when ASIC machines had not be designed for Litecoin Scrypt mining, anyone with a good enough GPU could profitably mine litecoin with the same computer they used at home, while they were off at work or asleep not using it. If you aren’t aware, GPUs (graphics cards) compute the kinds of functions necessary for mining at many times the speed that CPUs (core processors) alone would.
ASIC hardware stands for Application-Specific Integrated Circuit, which basically means a computer with no other intended use than mining. It used to be that the higher RAM requirements for mining Scrypt to get litecoin was a barrier to introducing ASIC machines for this purpose alone. Now, ASIC technology has evolved to the point where litecoin can be mined with it as well. Their design is intended to optimize the speed and power usage while performing only mining functions. These are generally going to be stand-alone units that only require a power source, but some do plug into an existing computer.
The most reputable ASIC miner for litecoin at the time of this writing appears to be the Bitmain Antminer L3, which is selling new for about $3,000 USD. It is hard to find ASIC miners that are used because they are generally going to be used until they are no longer profitable and obsolete. While at first litecoin prices were around the high $30s, various conditions caused Litecoin to tank and it traded around $3 USD for a few years. Now that Litecoin has been the first cryptocurrency to implement Segregated Witness (Segwit) and to successfully transact over a Lightning Network, buying is piling-in and driving the price up over $40 USD. It is likely for this reason that ASIC manufacturers started producing as many mining rigs for Scrypt in 2017 as they can.
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