When Bitcoin first started out, there weren’t a lot of miners out there. In fact, Satoshi, the inventor of Bitcoin, and his friend Hal Finney were a couple of the only people mining Bitcoin back at the time with their own personal computers.
Using your CPU (central processing unit—your computer’s brain and an integrated component in any computer) was enough for mining Bitcoin back in 2009, since mining difficulty was low. As Bitcoin started to catch on, people looked for more powerful mining solutions.
Gradually, people moved to GPU mining. A GPU (graphics processing unit) is a special component added to computers to carry out more complex calculations. GPUs were originally intended to allow gamers to run computer games with intense graphics requirements. Because of their architecture, they became popular in the field of cryptography, and around 2011, people also started using them to mine bitcoins. For reference, the mining power of one GPU equals that of around 30 CPUs.
Another evolution came later on with FPGA mining. FPGA is a piece of hardware that can be connected to a computer in order to run a set of calculations. They are just like GPUs but 3–100 times faster. The downside is that they’re harder to configure, which is why they weren’t as commonly used in mining as GPUs.
Finally, around 2013, a new breed of miner was introduced: the ASIC miner. ASIC stands for application specific integrated circuit, and these were pieces of hardware manufactured solely for the purpose of mining Bitcoin. Unlike GPUs, CPUs, and FPGAs, they couldn’t be used to do anything else. Their function was hardcoded into the machine.
Today, ASIC miners are the current mining standard. Some early ASIC miners even appeared in the form of a USB, but they became obsolete rather quickly. Even though they started out in 2013, the technology quickly evolved, and new, more powerful miners were coming out every six months.
After about three years of this crazy technological race, we finally reached a technological barrier, and things started to cool down a bit. Since 2016, the pace at which new miners are released has slowed considerably.