user78: 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?

user78: 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.

user323: 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.

78: <p>Bitcoin, on average, has a block every 10 minute. There are <a href="https://bitcointalk.org/index.php?topic=130222" rel="nofollow">advantages</a> (<a href="https://bitcoil.co.il/Doublespend.pdf" rel="nofollow">pdf</a>) 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).</p>

<p>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.</p>

<p>So, my question - are the known ASICs today compatible with changing the block speed?</p>
 78: <p>ASICs just calculate double SHA256 (using the correct data size of 80 bytes, and linking between the two hashes <a href="https://bitcoin.stackexchange.com/questions/7236/bitcoin-mining-asics-used-for-cryptographic-application-rainbow-tables/7264#7264">as described here</a>). 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.</p>
 323: <p>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 <code>timestamp</code> and <code>nonce</code> 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.</p>
