Quote:I can still get as low as 1us at CPU idle in DPC latency checker in windows 10 if I disable things in device manager. Namely if you disable your display adapter driver most of the periodic latency spiking issues disappear. The real problem is the OS changes themselves that took place after XP to GDI and direct X or the display drivers have changed for the worse. Just moving your mouse or using your keyboard to open and close the windows menu will cause DPC latency spiking and in nvidia inspector you can see that it triggers power state changes from P8 idle to P0 3D clock speeds.
From what I hear GPU boost in Nvidia bios is also a cause of some latency spiking. If you force power saving power states with Nvidia Inspector latency gets a bit worse too so seems like it's likely accurate. It's the same reason people disable c-states to minimize latency basically. TimerTool program can help minimize typical spiking severity if you modify timer to set timer to 0.5 ms. I went from around 1000us periodic spiking from light CPU load even from minor stuff like mouse/keyboard usage down to around 500us. It's a nice improvement and can be setup to run sent to system tray at startup with a registry tweak or bat file as well.
I can't fault DPC Latency Checker for any of those things and while LatencyMon is a good tool in it's own right and in some ways more informative it's not reporting any better latency results yet no one claims that is broken. Disabling other things can help too like network adapters and USB devices. Some people recommend turning off power saving features.
As far as HPET is concerned from what I've read about it's a crap shoot mix bag of results scenario where basically you can't have your cake and eat it too. For some tasks it will help and for others it will hurt essentially is how I interpreted how the differing timers work. It's kind of similar to adjust best performance of program or background services you can't have both ways and depending on the scenario one or the other is more ideal.