PG27AQDP missing option for 240 Hz ELMB

[Baker80k]

Hi all,

Recently got a PG27AQDP, enjoying it for the most part but I've encountered some strange behavior.

Under Windows settings, the normal framerates I'd expect are present, in that they're close to even fractions of 480: 479.99, 239.97, 119.88. However, there is also an option for 120 Hz. Normally I wouldn't think much of this but I've found that the 120 Hz option is the only one where ELMB actually seems to be working.

These images are in the ULTRAKILL sandbox. Left is strafing, right is strafing and panning. I'm using a controller so I know there's no polling rate funny business going on, and I am using PresentMon to track FPS so I know I can hold a consistent 600 uncapped.

479.99 Hz, ELMB off

479_comparison.png (2.05 MiB) Viewed 11867 times

239.97 Hz, ELMB on

239_comparison.png (2.23 MiB) Viewed 11867 times

120 Hz, ELMB on

120_comparison.png (2.5 MiB) Viewed 11867 times

As you can see, in all cases just strafing looks great, but with 479.99 and 239.97 as soon as there is any panning the STORE text becomes almost unreadable. This is the sort of thing I would expect ELMB to fix, and it does when selecting 120 Hz. However, there is no option to select 240 Hz in Windows settings, and I can see that selecting 119.88 Hz has similar motion clarity issues to 239.97. (The OSD shows 120Hz at 119.88 and 120, but the difference in quality is night and day)

So, my question is am I missing the Windows setting which allows ELMB to work properly at 240 Hz, and if so how would I go about fixing that?

Monitor firmware is MCM104

Things I have tried:
- Updated graphics driver
- Updated GPU firmware
- Turning DSC on or off
- Using DP 1.4 or HDMI 2.1