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Windows 7: DPC latency spikes heavily interfering with audio playback

13 Oct 2012   #1

Windows 7 Professional x64
DPC latency spikes heavily interfering with audio playback


After installing my new graphics card (ASUS nVidia GT640) and the drivers, I started experiencing extreme dropouts in audio playback with every player. Ran standard DPC checks and found that I was experiencing extreme spikes during graphics refreshes (e.g. scrolling through folders in Explorer). I definitively linked the spikes to the nVidia card/driver combo using LatencyMon and xperf, both of which listed nvlddmkm.sys and dxgkrnl.sys as the longest laggers by some distance (recorded latencies up to 50ms for nvlddmkm.sys using LatencyMon).

I've tried the usual stuff. SpeedStep is turned off from BIOS, recent BIOS version, driver updates all round (all to the latest appropriate versions, as far as I can tell), underclocked the GPU's memory and CPU clocks to the lowest possible setting, set lowest quality options for graphics, uninstalled all unnecessary hardware entries, reinstalled the graphics driver from scratch (as a corollary, VGA save mode has no noticeable latency, of course), disabled all other sound devices (esp. the HDMI audio on the gfx card).

Basically, does anyone have any ideas/thoughts/advice on what I can try before I ship this bad boy back to the retailer? Would be much appreciated.


Edit: USBPORT and ndis were also somewhat higher than expected. I know those are built-in drivers but I don't know what that means in terms of reducing the latency they cause. Advice on that would also be welcomed. Additionally, what would you say is the maximum acceptable latency you'd expect to see in the LatencyMon listing? I have about 10 @ ~4ms which is considerably higher than I would've thought they should be.

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 DPC latency spikes heavily interfering with audio playback

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