My system is a based on GA-EP45-ds4p motherboard with a intel q9550 and 8 gigs of ram runnig in WIN 7/64 environment. My problem started with serious frequent pops and distortion in playback audio and video. I tried an external usb (actually 2) sound cards and the problem persisted. I read through forums and discovered that the most common cause of my problems was long DPC (delayed procedure call) delays in excess of 500uS. I consistently had latencies in excess of 10000uS or 10mS. Digging around I discovered a comment of a forum for gigbyte motherbords and someone suggested that turning off speedstep and C1E in bios would fix the problem. I turned off C1E and low and behold my average latency dropped to 100uS!! Problem fixed. Is this a Gigbyte implementation problem or an inherent issue with using the enhanced power saving modes like C1E?
One further bit of info. I have two computers based on this motherborad and they both react identically. However I have an older core2 bnased system using the nvidia chipset that hase C1E enabled without issue. So motherboard design flaw?