One of my rigs has 8 1070's that have been running nicely for almost 4 years.  But something I have never understood is that overclocking the memory makes no difference to the hashrate. But increasing the core clock does.  It's precisely the opposite of what is supposed to happen.  My other rigs which have 1070ti's don't exhibit this behavior.

My 1070's are tuned to use around 110 watts hashing at around 28mh/s which seems pretty optimum but I only achieve this by leaving the mem clock alone and bumping up the core clock.  All my rigs hardware are identical excepting the 1070ti's on the other rigs, which I have running at around 110 watts and 32.3mh/s by increasing the mem clock.

I haven't bothered asking this before because I doubt very much there is an answer.  But has anyone experienced this and know what causes it?