Could try forcing Windows to use the HPET clock instead of the mixed APIC/TimeStampControl and such that are likely in use by default. This has supposedly been a fix of sorts for some stutter issues with SLI in the past in some scenarios as well. It's an old and often forgotten tweak that even up through Windows 8, never gets set up as the central timer out of the box (doesn't always improve things when legacy hardware is in play)---may be the same for Win10 as well.
Check the System Devices section of Device Manager to see if there is an instance of High Precision Event Timer installed---if so, it is already active in your BIOS and Windows installed it but may not be using it exclusively. If not present, check your BIOS to see if you have the option to enable it there. Once you can confirm it is installed in Device Manager, you can force Windows to use it exclusively. It is a higher resolution timer than most other options and thus (in theory) provides better synching across multiple devices.
To force Windows to use it, run this command from an administrative CMD prompt and then reboot:
Code:
bcdedit /set useplatformclock true
To unlock it and set it back to using the mixed timers again, run this from an admin CMD prompt and reboot:
Code:
bcdedit /deletevalue useplatformclock
There used to be a tool floating around where you could verify the clock speed and such, as well as a button to click for enable/disable HPET. Will dig around to see if I can find a link for it.
Edit:
Uggh... looks like Win10 is doing something different when it comes to the synching. Just another monkey wrench thrown into the mix. Basically...it's gonna depend on your specific rig on whether using HPET exclusively, as part of the mix, or disabling it entirely (both Windows and then BIOS) will help improve things. Here's a link from an overclock site where it was being discussed:
Windows 10 - disable HPET before install and enjoy low latencies!
It has a link to a Harmonic app that will display your timer's resolution as well as allow you to toggle HPET on/off exclusively. Used it to toggle it off then back on for my Win8 x64 laptop and it works to turn it on and off. The app passes the BCEDIT commands, so you may need to run it as admin for it to work properly (just instinctively right-clicked it when I ran it). The download page has links at the bottom to external sources from Microsoft about the timers for those who want to get their geek on about the topic.