Hey, I just built my new systems last week with a sapphire 6870 and it shows as 283.5 Mhz max memory clock in GPU-Z 0.4.7 for me as well but as the card is performing as expected I assume its because GPU-Z does not fully recognize the HD 6XXX yet. I think it is purely a calibration issue with the sensor reading with the software, thats fair enough as its a 3rd party program and should be sorted soon.
CPU-Z 1.56 barely displays anything about these cards.
I would suggest checking CCC settings for any performance shortcomings, I had a performance hit when I allowed the drivers to scale the display resolution during my tinkering.
I have not tried GTA so cannot comment on that but if you get 15-16k score in vantage its as intended I would assume.
edit* - I have win7 64bit and using the official 10.10 drivers (no hot fix)
CPU-Z 1.56 barely displays anything about these cards.
I would suggest checking CCC settings for any performance shortcomings, I had a performance hit when I allowed the drivers to scale the display resolution during my tinkering.
I have not tried GTA so cannot comment on that but if you get 15-16k score in vantage its as intended I would assume.
edit* - I have win7 64bit and using the official 10.10 drivers (no hot fix)