A machine running at 200 TH/s (terahashes per second) makes about 200 trillion attempts every second. That is trillions of attempts before you finish saying “Bitcoin.”
You can hear the fans. You can feel the heat. But the thing all that machinery is trying to produce is just a number.
Think of a drawing with an enormous number of possible tickets
Picture a prize drawing, like a lottery, where each attempt is one ticket. Each attempt produces a hash: a number calculated from a block header. The header is the short summary at the top of the block the miner hopes to add. For Bitcoin’s proof of work, the miner runs the header through SHA-256, a standard hashing formula, twice. Bitcoin’s rules set a number called the network’s target. The result must be at or below that target to qualify.
The drawing idea only goes so far. No organizer pulls a winning ticket from a hat. Anyone can calculate the hash and check whether it qualifies.
A failed attempt does not get you closer
After each attempt, the machine changes a small part of the header that it is allowed to change. Then it tries again. When those changes run out, the mining software prepares new header data. Every change gives a new attempt.
After a long losing streak, the miner is not “nearly finished.” It has not filled in ninety-nine percent of a puzzle. With the same target, the next attempt has the same chance as every attempt before it. Hashrate is the number of attempts a machine makes per second. More hashrate means more chances each second. It does not promise that the next attempt will win.
Here is the clever part
Finding a hash that qualifies takes a huge amount of searching, on average. Checking one is quick. Another computer calculates that one hash and compares it with the target. Nobody has to repeat all the failed attempts.
So the network can see that the work was done without taking the miner’s word for it. The chips are not cracking codes or decrypting people’s payments. They are only searching for a block-header hash that qualifies.
Now the numbers on your dashboard mean something
A terahash per second (TH/s) is a trillion attempts per second. A petahash is a thousand terahashes. An exahash is a thousand petahashes.
When one hashboard stops hashing, some of those attempts disappear. Antminer logs call each hashboard a “chain.” Getting those attempts back matters. But follow the work all the way through. A healthy hashrate on the miner’s own web page is not enough. The miner also needs fresh work from its pool, and its results must reach the pool. A pool is a service where many miners work together and share the rewards. A later lesson explains pools.
Optional reading for this lesson
Continue your study
Reading for this lesson
Block construction and proof of work.