Bitcoin Forum

Sorry for being stupid but I don't get how this works. If you choose a noonce and hash it with a block's contents, wouldn't it take longer to do this for a second, third, fourth (etc) blockchain? I know I'm must be missing something simple about how this works... Thanks in advance

It sees is the nonce will work for any of the other blocks. Instead of doing the same work twice for Bitcoin and Namecoin it sees if the one nonce will work with either.

the same proof of work is valid for both blockchains, no extra work is done by your gpu, but the work that is done is submitted to 2 places
ie bitcoind and namecoin
if it costs anyone anything it is the pool software checking twice, not the gpu doing extra work :)

Thanks guys, but I still don't get it. Can you walk me through it step by step? I thought solving a block was just a guess-and-check, so my thinking is that the "check" step is what takes all the computational resources. So by "checking" two different chains, you're doubling the cost.

Obviously I'm wrong, can someone clear up my misunderstanding? Thanks!

"Guess" is what takes up all the resource, "check" is easy and doesn't require much at all.

"Difficulty" is in reference to how low a number must be before it is valid, the smaller the number the larger the difficulty. Since the Namecoin difficulty is lower than Bitcoin difficulty, that means that any Bitcoin block solutions are automatically also valid for Namecoin because they are equal to or better than the required difficulty.

Guys, please check out and improve the wiki. https://en.bitcoin.it/wiki/Merged_mining#Sharing_work is the closest I found. Rather than explain it again and again, let's build the wiki into a goto resource for FAQs like these.