Guys, I am NOT talking about overclocking at all. I am specifically talking about the maximum out of box boost clock speeds (call it GPU Boost 2.0/3.0) of identical GPU models. Yes, temps and power are a limiting factor and can impact the observed boost clock speeds, but really it's not at all difficult ti determine your maximum out of box boost speed.
Read this article. Eleven EVGA Reference GTX 980 Ti. The higher the ASIC, the higher the observed out of box maximum boost clock speeds.
http://ocaholic.ch/modules/smartsection/item.php?itemid=3946
Show me proof that two GPUs of the EXACT SAME MODEL, where the one with the higher ASIC has lower out of box maximum boost clock speeds.
Sometimes, this value may be different due to different BIOS versions, and sometimes I have seen a lower ASIC card get a slightly higher max voltage to compensate for the lower bin (but the higher voltage would only account for one extra bin)...but for all intents and purposes for the GTX 900 Maxwell series, for two identical GPUs, a higher ASIC meant a higher maximum out of box maximum GPU Boost 2.0 clockspeed. I would love to be proven otherwise.