The DPC Latency Checker no longer works properly since Windows 8 because Microsoft changed the kernel timers.

A successor version that supports current versions of Microsoft Windows has not been released yet.

Instead, it is better to use LatencyMon: https://www.resplendence.com/latencymon

I would use LatencyMon because it shows which driver is causing too high DPC latencies (if this is the issue).

Other reasons might be power saving in nVidia graphic cards, which can be turned off with a tool called powermizer.

This solved audio drops on my system which were not even visible with LatencyMon, which made this issue very nasty.
I stumbled only by occasion over a thread about system optimization in Steinberg's Cubase forum, where this was mentioned.

I know you didn't mention audio drops, but who knows where those latency spikes are coming from .. maybe it helps.

What energy profile are you using?

Did you disable power saving in the BIOS? C-States and if applicable P-States and T-States? C1N?
Did you disable clock spread spectrum?
You can also try to enable TURBO, but to disable Speedstep. Sometimes you end up with such settings with a base clock which is around 200 MHz higher.

This is what I did in my BIOS settings: https://www.tonstudio-forum.de/blog/Ent … -X10SRi-F/

EDIT: on the other hand, if you don't encounter any audible problems (audio dropouts), then you can just ignore it. If you only play music, then you don't need low ASIO buffer sizes and can simply use 1024 or even the maximum value, which relieves the CPU the most.

FYI, after disabling ipv6 and setting nvidia power to "adaptive", running LatencyMon for 18s while playing music to the RME, I get:

iusb3xhc.sys - Intel(R) USB 3.0 eXtensible Host Controller Driver
isr 143661
dpc 151561
highest ms 0.224080
total 1612.663443

for comparison:
nvlddmkm.sys - NVIDIA Windows Kernel Mode Driver, Version 441.66
0
134
0.049650
0.749833