<p>The miner can change the block header hash several different ways:</p>

<ol>
<li>Change the timestamp. This is the least intrusive, but works just fine. If you can do more than 4 Th/s, this starts to become a problem.</li>
<li>Add transactions. Adding any new transaction changes the Merkle root, so this gives you entirely new nonce spaces.</li>
<li>Change the coinbase transaction. This is the most common method. 32 bits are typically used to act as an additional nonce.</li>
</ol>

CC BY-SA 3.0
2016-07-20T21:25:39.173Z
How can a miner change the coinbase transaction? More specifically, does this changeable field mean anything?
galahad
CC BY-SA 3.0
2016-07-20T23:00:07.070Z
The scriptSig field of the coinbase transaction's txin can contrain 96 bytes of freeform data.
Pieter Wuille
CC BY-SA 3.0
2016-07-20T21:16:58.083Z
2016-07-20T21:16:58.083Z
Jimmy Song
<p>Since nonce is a 32 bit number, the maximum value of nonce can only be 4,294,967,296. So, if a miner doesn't find the target hash within this number, what happens?     </p>

CC BY-SA 3.0
2016-07-21T17:34:07.500Z
Note: Although a signed 32-bit integer's max value is 2^32 - 1 = 2,147,483,647, that's not really relevant: The miners will iterate through all 32-bit values, so they have 4,294,967,296 tries really. Put another way, think of that 32-bit number as an unsigned integer.
Alin Tomescu
<mining-theory><nonce>
Maximum # of hashes for finding a block?
galahad
# Maximum # of hashes for finding a block?

(Asked by: username_0 on 2016-07-20)

Since nonce is a 32 bit number, the maximum value of nonce can only be 4,294,967,296. So, if a miner doesn't find the target hash within this number, what happens?

**Tags:** mining-theory, nonce

> **Comments:**
> **username_1**: Note: Although a signed 32-bit integer's max value is 2^32 - 1 = 2,147,483,647, that's not really relevant: The miners will iterate through all 32-bit values, so they have 4,294,967,296 tries really. Put another way, think of that 32-bit number as an unsigned integer.  

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## 1 answers

### Answer by username_2 on 2016-07-20. Score: 6 | Accepted answer

The miner can change the block header hash several different ways:

1. Change the timestamp. This is the least intrusive, but works just fine. If you can do more than 4 Th/s, this starts to become a problem.
2. Add transactions. Adding any new transaction changes the Merkle root, so this gives you entirely new nonce spaces.
3. Change the coinbase transaction. This is the most common method. 32 bits are typically used to act as an additional nonce.

> **Comments:**
> **username_0**: How can a miner change the coinbase transaction? More specifically, does this changeable field mean anything?  
> **username_3**: The scriptSig field of the coinbase transaction's txin can contrain 96 bytes of freeform data.  

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