NVIDIA cards that have Boost, along with temperature throttling and the stock BIOS with set power limits, it doesn't reflect the true potential overclockability of a card based on the ASIC until you modify the BIOS.
The same thing with temperature throttling on AMD cards and voltage limits.
I guess the ongoing theory is, the higher the ASIC (closer to 100%), the closer to specifications the circuitry is, thus you get the lower voltages required for a set clock speed. Basically, the card is more efficient, so it's better for air cooling since it meets the specified clock speeds at a lower voltage.
The lower the ASIC, the card isn't as efficient, so watercooling is recommended because more voltage is needed, thus driving up temperatures, which could cause issues like temperature throttling on air.
Most people assume that lower ASIC means better overclockability, but that's just speculation.
In my opinion, ASIC has no bearing on overclockability potential. Overcockability potential is based on the GPU, and the GPU alone. The best way to test for this is to find a graphics card with close to 100% ASIC, modify the BIOS, and find the most stable overclocks and log the voltage. Then, remove the GPU, put it on a card that has something like 60% ASIC, and see how it compares. My assumption is that the GPU will reach the same overclocked clock speeds, but it will need a higher voltage to get there.
Edited by El_Capitan, 02 January 2016 - 09:05 AM.