LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

[k2viper]

Only VT through Nvidia CP.
Did you found other stable settings?

E.g. I found for 240hz VT >1302 is a bit unstable - screen may randomly lose sync (go black and back again), but after some warming up it keeps running stable.
My old VG278H sometimes didnt start up if VT was higher then 1173, but warmed up, it runned at 1180. I think there is the same edge of stability here.

[dogroll]

No I found the same settings as you via CRU, max 1582 VT before needing to restart to safe mode to reset CRU display entries because black screen.

I haven't messed with VT at 240Hz, because I am not sure about it. For 144Hz it makes sense, when I open CRU there's already a 144Hz 'detailed resolution' to edit, which affects the 144Hz option listed in windows display settings. However there doesn't exist 120Hz or 240Hz options -- if I make a new entry for these resolutions, would it affect the already existing 120 and 240Hz options in windows display setting? Because it doesn't make a new listing there.

[k2viper]

240hz resolution is under the extensions block (bottom block of the CRU main page).

You definitely will change an existing resolution, when you're editing any standard (120, 144, 240 etc) refreshrate resolution, since you would not have two 144hz resolutions in your list.

I've reinstalled nvidia driver yesterday, I suppose that blackscreen-and-back behavior after cold boot is much GPU driver related, because it triggers only on desktop, when windows Aero is kicking in. Perhaps my mixed NvidiaCP+CRU experiments broke something in driver or its display modes

[dogroll]

Think there's a bug with the firmware on this monitor :/

When switching from 240Hz with freesync to 240Hz with MBR, there is some stutter (very obvious when moving mouse cursor or looking at testufo.com). The stutter has a consistent cadence which suggests it's some sort of judder to do with strobe and refresh rate mismatch.

I have to switch MBR off, go to windows display settings and switch to another refresh rate like 144Hz, then switch back to 240Hz and then re-enable MBR, to get normal operation. So switching from 240Hz with freesync to 240Hz with MBR is a painful procedure on this monitor.

I have used reset-all.exe that comes with CRU and restarted PC just to confirm that messing with that didn't cause the issue.

[k2viper]

I think I've seen some of the behavior you're describing while experimenting with different custom refreshrates and VTs, but in my case it was not so painful. If I got these stutters, switching mode from 240 to 144 and back again fixed it, I'm not even sure that is monitor related, not simple browser stutter. Also power-cycling may help.
I just havent tried Freesync (since I'm a nvidia gpu user), so I cant confirm exactly your case of behavior.

[k2viper]

When switching from 240Hz with freesync to 240Hz with MBR, there is some stutter (very obvious when moving mouse cursor or looking at testufo.com). The stutter has a consistent cadence which suggests it's some sort of judder to do with strobe and refresh rate mismatch.

How do you reproduce this? Enable freesync (MBR off and greyed out), then disable freesync (MBR off but not greyed out), then enable MBR and stutters appear after you enable MBR, or they appear just after you disabled freesync?

Is it tick-tick-tick stutter/judder like every 0,5 sec, or its an "unsmoothness"? I described some of these in this post: viewtopic.php?p=30673#p30673 and after this I found that these stuttering was due to frameskipping.

When you get this stuttering, check it for frameskipping, just curious is this the real cause, or its strobe-sync related.
Anyway, such stuttering is probably a bug because you dont mess with overclocked refreshrates and VT's as I did.

[dogroll]

How do you reproduce this?

Simply put the monitor in 240Hz regular mode (freesync or not, just MBR disabled), then switch it to MBR via the OSD, and the stutter will occur. Not always, and just now trying to reproduce it I had to try about 7 times to get the 'bug' to happen, but before it was happening very often.

I took a crappy video on my phone to show the stutter: https://streamable.com/kwd8v

[k2viper]

Simply put the monitor in 240Hz regular mode (freesync or not, just MBR disabled), then switch it to MBR via the OSD, and the stutter will occur. Not always, and just now trying to reproduce it I had to try about 7 times to get the 'bug' to happen, but before it was happening very often.

Oh, I havent tried to switch MBR back and forth too often Personally i rarely switch MBR off.
In your case it could be more annoying since you're a freesync user.

Looked at video - yes, I definitely saw that kind of stuttering while experimenting with nonstock VTs/refreshrates.

[k2viper]

Think there's a bug with the firmware on this monitor :/

When switching from 240Hz with freesync to 240Hz with MBR, there is some stutter (very obvious when moving mouse cursor or looking at testufo.com). The stutter has a consistent cadence which suggests it's some sort of judder to do with strobe and refresh rate mismatch.

I have to switch MBR off, go to windows display settings and switch to another refresh rate like 144Hz, then switch back to 240Hz and then re-enable MBR, to get normal operation. So switching from 240Hz with freesync to 240Hz with MBR is a painful procedure on this monitor.

I have used reset-all.exe that comes with CRU and restarted PC just to confirm that messing with that didn't cause the issue.

I think I found a workaround/fix for this issue.
This is the default 240hz timings.
Look at the refresh rate, it's 239,759hz. Round it and replace with 239,760hz - this rate is also stated at the user's manual.

Post your experience please.

[dogroll]

Think there's a bug with the firmware on this monitor :/

When switching from 240Hz with freesync to 240Hz with MBR, there is some stutter (very obvious when moving mouse cursor or looking at testufo.com). The stutter has a consistent cadence which suggests it's some sort of judder to do with strobe and refresh rate mismatch.

I have to switch MBR off, go to windows display settings and switch to another refresh rate like 144Hz, then switch back to 240Hz and then re-enable MBR, to get normal operation. So switching from 240Hz with freesync to 240Hz with MBR is a painful procedure on this monitor.

I have used reset-all.exe that comes with CRU and restarted PC just to confirm that messing with that didn't cause the issue.

I think I found a workaround/fix for this issue.
This is the default 240hz timings.
Look at the refresh rate, it's 239,759hz. Round it and replace with 239,760hz - this rate is also stated at the user's manual.

Post your experience please.

I made this change (which results in the 'actual' refresh rate becoming 239.764Hz) and that caused judders every few seconds instead of every 0.5s or so.