Apparently HBM overclocking is currently disabled by AMD.
QUOTE
AMD will not allow you to overclock the memory when the first Fiji cards are released. AMD feels that the memory technology is too new and there is more than enough bandwidth, so they are locking down the ability to overclock the memory in AMD Overdrive. This might change down the road, but for the time being only the core clock can be overclocked by end users.
Sauce:
QUOTE(cstkl1 @ Jun 19 2015, 10:05 AM)
Whats the magic on 390x other than faster vram???
Its beating 980.
Although most reviews using overclocked 50mhz units.
I trust hardwarecanucks more than anybody else.
980 20-30percent lead gone.
Which benchmark you looking at? MSI 390x is clocked at 1100/1500, at that clock it's definitely faster than a stock 970 and close to 980 and at 4K it definitely on par or slightly faster than 980 in some games.
Most of the reviews didn't provide enough info, no average boost clock for Nvidia cards, no exacts settings for the game their tested.
I haven't tested the latest official beta driver but it's pretty similar to modded win10 driver i'm currently using. That driver have much less driver overhead compare to previous 15.5 and below.
I'm waiting for HardwareCanucks too and hoping they will include average clock speed graph like they did with 960 reviews.