Puzzled by DPC latencies


I noticed that in my Vista 32-bit I have strangely high DPC latencies (something is peaking oftenly 1000us viewed in DPC latency checker)
However my system seem working smoothly (games and everything). I disabled all unecesarry drivers, but
"problem" still remains (even in emergency mode).

xperf indicates max duration of DPC CPU usage
ntkrnlpa.exe - 69us
ndis - 67us
usbport.sys - 40us
nvmimx32.sys - 40us
nvlddmkm.sys - 30us
storport.sys - 30us
tcpip.sys - 26us
nvstor.sys - 19us
netbt - 15us
hdAudBus.sys - 14us
netio.sys - 13
and so on.

If I sum all these max latencies it is not 1000us as shown in DCP latency checker.
Games, video music is fine with no glitches, but strange is Windows Photo Viewer, I I run presentation dxgkrnlg.sys is at max 1.3ms. There is problem that if I run presentation for some time (presentation is not running smoothly, but image changes are stuttering) something freaks out and fires TDR which ends by bsod because Nvidia driver can not recover. I do not know if it is related or not ...

Other thing is that my Vista 32-bit is high latency and Vista 64 low latency always running about 40us (as seen in DPC checker).

Any hint or so?

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