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BenQ XL2720Z overclocked to 220Hz and 250Hz [SUCCESS!]

Talk about overclocking displays at a higher refresh rate. This includes homebrew, 165Hz, QNIX, Catleap, Overlord Tempest, SEIKI displays, certain HDTVs, and other overclockable displays.

Re: BenQ XL2720Z overclocked to 220Hz and 250Hz [SUCCESS!]

Postby loopy750 » 21 May 2019, 03:09

Chief Blur Buster wrote:Did some more research.

OK,
- I found out the NVIDIA drivers, is indeed, using 6bpc. You're right on that count.
- BUT my current NVIDIA drivers is apparently doing GPU-side temporal dithering. Neat. GPU-side FRC!

Today I learned, temporal dithering is a feature of NVIDIA graphics drivers, permanently turned on by default on Windows systems. This is a little-known feature that NVIDIA graphics drivers already is doing an FRC equivalent. There's even a little known hack to disable NVIDIA temporal dithering. Nontheless, this explains why I'm seeing 8-bit color depth with 6bpc GPU output.


I'm using a GTX 1070, and reading what Nvidia control panel "Output colour depth" says.

Testing 165Hz (8-bit), the gradient image looks as it should.
Testing 166Hz (6-bit), the gradient looks much the same but I think I can see FRC at work. When looking closely, the grey parts appear to be slightly flickering/static, which must be the GPU-side dithering at work.

Found a post here that allows you to alter or disable dithering for the Nvidia driver.
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Re: BenQ XL2720Z overclocked to 220Hz and 250Hz [SUCCESS!]

Postby Falkentyne » 21 May 2019, 13:26

loopy750 wrote:
Chief Blur Buster wrote:Did some more research.

OK,
- I found out the NVIDIA drivers, is indeed, using 6bpc. You're right on that count.
- BUT my current NVIDIA drivers is apparently doing GPU-side temporal dithering. Neat. GPU-side FRC!

Today I learned, temporal dithering is a feature of NVIDIA graphics drivers, permanently turned on by default on Windows systems. This is a little-known feature that NVIDIA graphics drivers already is doing an FRC equivalent. There's even a little known hack to disable NVIDIA temporal dithering. Nontheless, this explains why I'm seeing 8-bit color depth with 6bpc GPU output.


I'm using a GTX 1070, and reading what Nvidia control panel "Output colour depth" says.

Testing 165Hz (8-bit), the gradient image looks as it should.
Testing 166Hz (6-bit), the gradient looks much the same but I think I can see FRC at work. When looking closely, the grey parts appear to be slightly flickering/static, which must be the GPU-side dithering at work.

Found a post here that allows you to alter or disable dithering for the Nvidia driver.


Hi,
You are right that sometimes my timings does give frameskipping (a lot of it) and I have to press the S-switch a few times to get rid of it. But the timings you posted (at least on AMD hardware) give it every 2 seconds, 100% of the time. I'll see if I can find a more reliable VT with the settings I posted; sometimes just an increase or decrease of 1 helps, but those were based on the "lightboost" VT range of 1497-1502 for 85hz/100hz and 120hz.

Actually those first timings I posted seem to be even less reliable. I'm testing HT:1999, VT 1091 right now and it seems to be "clear" more often, or massive stutters. Only had an instance of the 2 second stutters a few times. I'll keep testing to see if I can find something that is more reliable for AMD users or if I have to stop here. ToastyX CRU is not allowing me to reduce the vertical total below 1088 right now either.

*Edit*
Finished my testing.
Went back to 1984/1094 and it seems stable *IF* i close all of the display dialog boxes!
Wasn't having this issue testing 120hz. PEBKAC moment I guess.
I do have an Accell DP 1.2 cable even though it's 10 feet so I don't think that's the issue. I'll play some more games and test some more stuff later.
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Re: BenQ XL2720Z overclocked to 220Hz

Postby saw141 » 27 May 2019, 13:46

This is absolutely amazing. Fantastic research and experimentation, this is what this website was made for, imo. I know it’s not PERFECT and completely stable but it’s awesome.

I actually sold my XL2720Z late last year and put it towards my current XL2740, I don’t regret the switch. I’ve been meaning to do a review of my XL2740 because it’s the best monitor I’ve ever used, it’s just the XL2720Z but with some more features. Apparently not exclusively 240hz over the XL2720Z, which is fine by me :x

Chief Blur Buster wrote:Range-unlocked gaming monitors with good electronics sometimes have unusually massive overclock headroom if hacks are found. 1ms TN panels are very overclockable if the electronics can keep up.


How would I go about safely testing XL2740 overclocks? Do you think that with a native 240hz, we could go higher? Even at lower resolutions like the 540p @ 480hz? I’m very interested in this, as long as I won’t destory my XL2740.
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Re: BenQ XL2720Z overclocked to 220Hz

Postby Chief Blur Buster » 27 May 2019, 17:00

saw141 wrote:How would I go about safely testing XL2740 overclocks? Do you think that with a native 240hz, we could go higher? Even at lower resolutions like the 540p @ 480hz? I’m very interested in this, as long as I won’t destory my XL2740.

Short answer: This unit is probably not overclockable above 240Hz.

Doubtful 480Hz can be achieved. Most 240Hz monitors have extremely little overclock headroom.

I suspect some may be able to reach 280Hz but the problem is that most early 240Hz monitors have scanrate-converting electronics, which means they are laggy at 144Hz and 60Hz because they scan-convert everything to 240Hz (buffering a 1/60sec slowscanning signal off the cable to scanout in 1/240sec), which makes many 240Hz panels slightly laggier for console gaming --

There's a finite time to refresh one pixel or pixel row at a time, from top to bottom -- that's the "scanout". See High speed video of scanout latency. Fixed-scanrate panels are nonoverclockable, it takes a scanout-synchronizing panel to be overclockable (panel line refresh at the same scan rate as the row-of-pixels being transmitted sequentially over the video cable (DisplayPort, HDMI, DVI, VGA, etc) -- all video cables, GPUs and monitors rely on sequential raster delivery (even for variable refresh rate!). Now, the interesting quirk is some panels have a fixed scanrate, which means electronics need to scan convert the delivery scanrate (GPU->cable->monitor input) to the panel scanrate (monitor input->monitor electronics(scaler/TCON)->panel). Most early 240Hz monitors scanrate-convert anything that's not 240Hz.

The best candidate for refresh-rate overclocking is probably the 23.8" panel used in the XG248Q, since that one is horizontal scanrate multisync (not a scan-converting 240Hz panel like most).

The best panels to overclock are the ones that realtime syncs panel scanout to cable scanout (minimal line buffering), without any buffered scan-conversion programming. For those who do not understand scanout, see High Speed Videos of LCD Scanout.
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Re: BenQ XL2720Z overclocked to 220Hz and 250Hz [SUCCESS!]

Postby saw141 » 27 May 2019, 18:40

Thank you Mark. As long as it’s “safe” (just because I can’t risk my hardware) I’m willing to try any experimentation with the XL2740. In a thread a few months I took advice from several people here about the hidden menu and settings and tweaked it, some.
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Re: BenQ XL2720Z overclocked to 220Hz and 250Hz [SUCCESS!]

Postby Chief Blur Buster » 27 May 2019, 18:58

Refresh rate overclocking has generally not harmed displays -- the display will generally glitch long before anything remotely overheats.

Certainly other things will be a risk such as bugs in voltage-boosted strobe backlights (Blur Reduction, DyAc, ULMB, etc) that are triggered during nonstandard modes (large VTs or refresh rate overclocking) like in the very early firmwares of XL2720Z. But that does not affect later firmwares nor the XL2740.
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Re: BenQ XL2720Z overclocked to 220Hz and 250Hz [SUCCESS!]

Postby remka56 » 04 Jun 2019, 09:51

help pls ! how to overclock the monitor to 250 hz ? i play cs go, amd card, firmware v003 , use cable dvi. Image
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Re: BenQ XL2720Z overclocked to 220Hz and 250Hz [SUCCESS!]

Postby RealNC » 04 Jun 2019, 10:37

remka56 wrote:help pls ! how to overclock the monitor to 250 hz ?

There's a screenshot in the first post of this thread. Have you tried that?
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Re: BenQ XL2720Z overclocked to 220Hz and 250Hz [SUCCESS!]

Postby remka56 » 04 Jun 2019, 11:14

RealNC wrote:
remka56 wrote:help pls ! how to overclock the monitor to 250 hz ?

There's a screenshot in the first post of this thread. Have you tried that?


tried writes Out Of Range
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Re: BenQ XL2720Z overclocked to 220Hz and 250Hz [SUCCESS!]

Postby Chief Blur Buster » 04 Jun 2019, 14:15

remka56 wrote:tried writes Out Of Range


Please re-read:
250Hz was achieved by setting both vertical porch and sync to 1, as due to the DisplayPort bandwidth limit, that was really pushing it to the limit - maybe even slightly too far - and I wouldn't recommend it. Not to mention how much worse YCbCr422 looks compared to RGB, IMO, which is why I consider 220Hz the practical limit, and somewhere between 240-248Hz if YCbCr422 doesn't bother you.


If you keep trying 250Hz, don't forget to
(A) Properly reconfigure the porches
(B) Properly reconfigure to YCbCr422

That said, 6-bit RGB looks better, and NVIDIA graphics drivers already does temporal dithering to create 8-bit GPU-side (albiet not necessarily as good as monitor's built-in FRC).
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