Nonce
A nonce is a field in the block header that a miner changes on every attempt. Change the nonce and the hash changes, and that repeats until it lands under the target.
What a nonce is
The asic cannot touch the other header fields: the link to the previous block, the transaction fingerprint and the target are all fixed. The nonce is what stays free, and that is what gets iterated. One substituted number is one attempt, and the hash from each attempt comes out completely different.
The catch is that the field is short, all of 32 bits, which is about 4.3 billion variants. An Antminer S21 at 200 TH/s sweeps that whole range roughly forty six thousand times a second. One nonce lasts a miner microseconds.
That is why the nonce is not the only thing being iterated. The pool hands miners different extra pieces (these are called the extranonce), the timestamp changes, and some firmware runs through the block version field as well. This trick is what AsicBoost is built on: the same asic checks more variants for the same watt.
The practical meaning for an owner is simple. A nonce is not a setting and not something you can turn in the interface. Knowing about it helps you see where the gain from custom firmware comes from and why a pool has to split the work between miners instead of handing everyone one job.
Quick reference table
| What it is | the field in the block header that gets iterated |
| Size | 32 bits, about 4.3 billion variants |
| S21 at 200 TH/s | sweeps the range about 46 thousand times a second |
| What else gets iterated | extranonce, time, the version field |
| Related to | AsicBoost, pool jobs |
Where the AsicBoost gain comes from
Iterating the version field gives the nonce one more degree of freedom. The asic spends less time recomputing the unchanged part of the header, and the same watt buys more checked variants.
We have builds like this for 28 models out of the 212 in the catalog, and the firmware holds a fee of 2.8 percent for its work, taken in hashrate rather than in money: a miner at 100 TH/s sends 97.2 TH/s to your pool.
The gain is neither endless nor free. It shows up where the pool supports this mode, and it does not repeal physics: pushing the clock still raises draw faster than it raises output.
An example in numbers
The nonce range is about 4.3 billion values. An asic at 200 TH/s makes 200 trillion attempts a second, so it walks the entire range around 46 thousand times within that same second. Hence the need for extra fields: without them miners would be computing the same thing in circles.
Related terms
Where to go next on the site
Software
- Software firmware
- HashCore Toolkit firmware
Algorithms
- SHA-256 algorithms
Hardware
- Antminer S21 tool
Questions and answers
Can the nonce be configured
No, it is an internal protocol field. It does not appear in the asic interface, and there is nothing there to touch.
Why is one nonce not enough
It is only 32 bits, about 4.3 billion variants. A modern asic walks that range tens of thousands of times a second, so the extranonce, the time and the version field come into play.
Is AsicBoost overclocking
No. Overclocking raises the clock and the draw, while AsicBoost changes the way the header is iterated. They are different things, and they work independently.
How the terms connect
Every link in the chain is clickable. Orange marks where you are now.
Looking for an ASIC miner
The catalog holds 212 models. You can compare them by hashrate and by joules per terahash, then plug your own rate into the calculator and see what stays in your pocket.
Page written and checked by Denys Klimchuk. Updated .