majnu wrote: ↑25 Aug 2021, 06:05
1) I didn't want to play in Fullscreen/Fullscreen Exclusive mode as I ALT+TAB whilst gaming and I didn't want to have the window minimize all the time. Although this did also fix the problem.
2) Buying the same monitor with matching refresh rate was off the table due to costs.
3) I settled on buying an Active Dual Link DVI-D to Display port cable (Bizlink XT625). It only cost £30 new and I thought it was a good deal compared to others online. This allowed me to connect my monitor to the graphics card's Display Port and select the 120Hz max refresh rate. The latency has much improved although ideally I should use matching monitors unless Windows changes their DWM as you described.
Sometimes the EDIDs are slightly different (120.001 Hz versus 120.034 Hz) so overriding the EDIDs with exact numbers would be ideal.
If you use outputs from the exact same GPU, and override the monitor's EDIDs with the exact same numbers in ToastyX CRU or NVIDIA Custom Resolution.
...Then NVIDIA GPU automatically synchronizes both of their outputs to be perfectly synchronous.
And it's essentially a simultaneous VSYNC event for both monitors.
And consequently, the single-Hz Windows compositor doesn't slew out of sync with one of the monitors.
Just edit the "Hz" number while using "Automatic", to EDID-override what the monitor's plug-and-play signalling does, so both monitors are on
exactly the same Pixel Clock, necessary for perfectly synchronous GPU output for multimonitor running in non-FSE.