On 11 May 2016 at 12:36, Henning Kopp <henning.kopp@uni-ulm.de> wrote:

On Wed, May 11, 2016 at 11:21:10AM +0200, Jannes Faber via bitcoin-dev wrote:
> On 11 May 2016 at 05:14, Timo Hanke via bitcoin-dev <
> bitcoin-dev@lists.linuxfoundation.org> wrote:
>
> > There is no way to tell from a block if it was mined with AsicBoost or
> > not. So you don’t know what percentage of the hashrate uses AsicBoost at
> > any point in time. How can you risk forking that percentage out? Note that
> > this would be a GUARANTEED chain fork. Meaning that after you change the
> > block mining algorithm some percentage of hardware will no longer be able
> > to produce valid blocks. That hardware cannot “switch over” to the majority
> > chain even if it wanted to. Hence you are guaranteed to have two
> > co-existing bitcoin blockchains afterwards.
> >
> > Again: this is unlike the hypothetical persistence of two chains after a
> > hardfork that is only contentious but doesn’t change the mining algorithm,
> > the kind of hardfork you are proposing would guarantee the persistence of
> > two chains.
> >
>
> Assuming AsicBoost miners are in the minority, their chain will constantly
> get overtaken. So it will not be one endless hard fork as you claim, but
> rather AsicBoost blocks will continue to be ignored (orphaned) until they
> stop making them.

At least until a difficulty adjustment on the AsicBoost chain takes
place. From that point on, both chains, the AsicBoost one and the
forked one will grow approximately at the same speed.

No: you are still assuming AsicBoost miners would reject normal blocks. They don't now and they would have to specifically code for that as a reply to AsicBoost being banned. So there won't be two chains at all, only the main chain with a lot (more than usual) of short (few blocks) forks. Each forks starts anew, it's not one long fork. Therefore there is no "difficulty adjustment on the AiscBoost chain".

Now if they do decide to ban non-AsicBoost blocks as a response to being banned themselves, they're just another altcoin with a different PoW and no one would have a reason to use them over Bitcoin (apart from maybe selling those forked coins asap).

You're confused about what "longest" means as well: it's not just the number of blocks, it's the aggregate difficulty that counts: so AsicBoost would never become "longer" (more total work) either.

Hope this helps clear things up.

Jannes