I actually never saw a single 1080Ti running without crashing with mem above +500. Most of them have problem with +400...
OTOH , the only 2 GTX-1080 (Not Ti) I have can run with +700 without crashing.
with equihash: -My OC Strix supports +130 Core, +1020 Memony -
-My OC Aourus extreme extreme water: +80 core, and really little OC in memory
One thing to keep in mind - some cards have a FACTORY memory overclock.
I've seen Factory memory clocks on 1080ti models anywhere from 10000 (effective) to a hair over 11000
yes, that's because I prefer OC factory models. Overclocking in linux, specially remote, is a pain, and I'm not always able to get it.
EWBF: I get about 750 sol/s with the Aourus Extreme Waterforce, and 780 with the Strix.
I'm unable to squeze any additional performance from the Aorus overcloking, however the extra OC allows the Strix give the 780.