Say there's a fork with 51% of the hashrate going to the new version. I assume then that the hashrate of the new chain would be almost half of what it previously was for as long as other miners join the forked now official chain.

During this time will the difficulty be reduced in a way that it would provide huge rewards to the new chain miners ?

  • Wouldn't the reward per block stay the same? (As in, it's not related to the difficulty, but based on this: github.com/ethereum/wiki/wiki/Mining#mining-rewards) Jun 18, 2016 at 20:19
  • Yes, even if the reward stays the same as hashrate would halve the block time would probably raise and as difficulty is calculated on block time I guess that difficulty would go down. Am I completely wrong and just dream of easy block rewards to compensate dao loss 😭 Jun 18, 2016 at 20:22
  • Note that I may not be clear as what I ask. The point is not on raising rewards but on making blocks easier to mine because of the difficulty diminished. Jun 18, 2016 at 20:25
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    Yes, if the hashrate goes down, the difficulty will go down to maintain the same block time. If the block time is the same, then the rewards per unit of time will also be the same. The only way to get more rewards per unit time is to make the block time shorter, and doing that could probably cause other things to change. (For example, you'd get more orphaned blocks, which might mean changing the part of the reward algorithm that deals with uncle blocks.) Jun 18, 2016 at 20:42
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    Okay, I think I understand what you originally meant now :) (My bad.) Yes, a lower block time (because of reduced difficulty) would mean more rewards (because more blocks). Jun 18, 2016 at 21:10

1 Answer 1


Yes, the hashrate will be split and the difficulty on both ends will go down. A prominent example in the wild the the fork-off of the Ethereum Classic chain at block number 1920000, see table below (block number / Ethereum difficulty / Classic difficulty):

      #       ETH       ETC
1920000   62.41 T   62.41 T
1921000   57.01 T    0.83 T
1922000   56.80 T    0.56 T
1923000   57.26 T    0.49 T
1924000   58.30 T    0.49 T
1925000   58.60 T    0.54 T
1926000   59.42 T    0.46 T

While most of the miners were agreeing with the hard fork to protect the DAO investor funds, you can see that the overall difficulty of the Ethereum chain went down by more than 5 trillion.

  • Yes, since I asked this question we had a very clear wildlife example with the eth/etc fork. Thanks. Dec 28, 2016 at 18:29

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