Bitcoin, on average, has a block every 10 minute. There are advantages (pdf) to having a higher "clock rate", e.g. Litecoin's block every 2.5 minutes. I call "BitcoinX4" the theoretical blockchain that is achieved by speeding up block creation time (hardfork), without affecting the total number of coins (block reward reduced by a factor of 4).

It is conceivable that at some point in the future, a "split" or "hard fork" will be made in Bitcoin, such that its blocks will be generated with a different (higher?) frequency, possibly while keeping a mining majority. For this to happen (hash power majority), ASICs need to be able to crunch the new "BitcoinX4" chain.

So, my question - are the known ASICs today compatible with changing the block speed?

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    There are also disadvantages to a higher clock rate, like more block reorgs (and hence lost rewards for miners). While a change like this might be conceivable, it's not very likely. – eMansipater May 1 '13 at 5:13
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    @eMansipater - more lost rewards for miners doesn't affect a single miner's expected benefit. It's a slight disadvantage, yet, but the downside is practically zero for such a small speedup factor. Anyway, this question is about how we could mine such blocks, not whether it's a good idea or not. – ripper234 May 1 '13 at 6:42
  • since we're being technical, it would negatively affect miners having poorer latency with respect to new block discoveries, and overall provide very slightly less security for the same amount of hardware cost. Nonetheless, there's a reason this was a comment instead of an answer. – eMansipater May 1 '13 at 7:42
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    @ripper234 problem is that to be safe you don't need "6 confirmations", you need "1 hour of confirmations", which incidentally now is ~=1h. If you increase block speed, you'll need more confirmations to consider a transaction safe, hence you'll have gained next to nothing. – o0'. May 3 '13 at 8:22
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    @Lohoris - bitcointalk is down. I added a direct link to Meni's paper. bitcoil.co.il/Doublespend.pdf – ripper234 May 3 '13 at 13:44

Any mining device can be used without alteration for mining a specific alt-chain, as long as the chain's proof of work is the same (double-SHA), and the size, encoding and position of the timestamp and nonce fields is the same in a block. The latter ensures that devices that increment those fields internally would not be altering other parts of the block header. As block speed is not a part of the header but an external constraint put on the specific cryptocoin, ASICs and other devices should be able to mine such blocks without a problem.


ASICs just calculate double SHA256 (using the correct data size of 80 bytes, and linking between the two hashes as described here). They do not care about protocol rules regarding transactions. ASICs can be used to mine many potential Bitcoin alts/hardforks, as long as the core Proof of Work algorithm remains double SHA256.

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