I bought a HIS 5770 recently and am having a couple of issues. It gave me 7.4s for my gaming and graphics score on windows performance rating, but when I benchmark it at pcpitstop it says my video is only in the top 40 percent (my 3d video is in top 3). When I run AMD overdrive it says my video card is 300 mhz which unless i'm confused it suppose to be 850. My mobo bios is upto date and according to CCC my graphics card drivers are up todate. Is there a problem with win 7 and this card or do I have something in my bios set wrong? I'm a bit confused and angry at my video getting trumped by onboard graphics according to pcpitstop.
I think your system is OK.
First of all i don't trust Windows performance rating and benchmarks like you tested because the most important thing to check for VGA's performance is real time games so test some games and c heck whether your FPS i OK or not.
Also about the downclocking its normal,it downclocks too 300 in idle mode and goes to 850 in games.