Computers & Electronics

Help needed! LG GP850 cannot enable 2560 X 1440 at 144hz and 10 bit color depth, while LG GL83A can. Defective?

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[OP]
Deal Addict
Jan 22, 2009
3393 posts
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Help needed! LG GP850 cannot enable 2560 X 1440 at 144hz and 10 bit color depth, while LG GL83A can. Defective?

Hi guys. Need help here. I upgraded from GL83A to GP850, but noticed the following issue:

Using Display Port on AMD R9 390 and Win 10:

On GL83A, the system auto changes the resolution to 2560 X 1440 at 144hz and 10 bit color depth. Everything works.

On GP850, the system auto changes the resolution to 2560 X 1440 at 120hz and 10 bit color depth. The 2560 X 1440 at 144hz option does not show up at the "List All Modes" of Advanced display settings. I tried to update both drivers of my monitor and gpu. No luck. Still no 2560 X 1440 at 144hz option show up under "List All Modes" of Advanced display settings.
120hz.JPG

Finally I was able to solve this issue by creating a custom resolution at AMD Radeon Software:
cr.JPG
After that the 2560 X 1440 at 144hz option shows up under "List All Modes" of Advanced display settings:
144hz.JPG
Now here comes another issue, at 2560 X 1440 at 144hz, I cannot set the color depth to 10 bit. The AMD Radeon Software only has the 8 bit option:
8 bit.JPG

So at this moment, it's a choice between 2560 X 1440 at 120hz and 10 bit, or 2560 X 1440 at 144hz and 8 bit. It's so strange as my old GL83A can do 2560 X 1440 at 144hz and 10 bit without any issue. Is my GP850 defective? Or my R9 390 is too old so it's somewhat not supported by GP850?

Thanks in advance!
17 replies
Member
Feb 9, 2008
407 posts
329 upvotes
Vancouver, BC
Are you testing with the same cable?
[OP]
Deal Addict
Jan 22, 2009
3393 posts
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zerod wrote: Are you testing with the same cable?
Yes! Tried both DP cables that came with GL83A and GP850. Same result.
Member
Mar 15, 2004
381 posts
82 upvotes
Toronto
I have the same monitor but i have it connected via DisplayPort to a EVGA 3080
In my Nvidia Control panel, I'm able to select 2560x1440 144hz with 10bpc
Member
Mar 15, 2004
381 posts
82 upvotes
Toronto
Just did some quick research...

LG GL83A is not a true 10bit panel
R9 390 uses Displayport 1.2
1440p 144hz with 10bpc takes more bandwidth than what DP1.2 can handle so that's probably why it bumps you down to 120hz
[OP]
Deal Addict
Jan 22, 2009
3393 posts
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Jereina wrote: Just did some quick research...

LG GL83A is not a true 10bit panel
R9 390 uses Displayport 1.2
1440p 144hz with 10bpc takes more bandwidth than what DP1.2 can handle so that's probably why it bumps you down to 120hz
Good to know! Thank you so much for the help!!!
Deal Fanatic
Feb 16, 2006
5056 posts
2044 upvotes
Vancouver
As before...

Neither of those monitors are true 10 bit; both are 8bit +FRC to simulate a 10bit colour depth.


.
Member
Nov 20, 2014
278 posts
95 upvotes
Ottawa, ON
I have a LG GL83A and it works as expected, it is surprising the GP850 doesn't work like that out of the box. Have you tried to adjust your monitors settings through its hud?
[OP]
Deal Addict
Jan 22, 2009
3393 posts
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SizableSac wrote: I have a LG GL83A and it works as expected, it is surprising the GP850 doesn't work like that out of the box. Have you tried to adjust your monitors settings through its hud?
I tried but without any success. Maybe LG implemented something new in GP850 to prevent 1440hz at 10 bit via DP1.2. After reading Jereina's comment I googled a bit as well. DP1.2 does not have enough bandwidth to handle 144hz at bit, so I'm surprised GL83-A can do that.
Member
Nov 20, 2014
278 posts
95 upvotes
Ottawa, ON
braveblade wrote: I tried but without any success. Maybe LG implemented something new in GP850 to prevent 1440hz at 10 bit via DP1.2. After reading Jereina's comment I googled a bit as well. DP1.2 does not have enough bandwidth to handle 144hz at bit, so I'm surprised GL83-A can do that.
I highly doubt that they would specifically gimp anything with DP 1.2 on purpose. Doesn't everything using DP use Display Stream Compression (DSC) these days? I still think it is an issue with your setup even though it was working before.

List of issues to check after reverting to system defaults:
Change all monitor settings (G83A needs to have DP 1.4 enabled specifically otherwise it is only using the 1.2 standard)
Monitor mode preventing specific color/res options?
Have you tried another DP cable?
What does your Display Specs say in Radeon Software? I also dont see pixel format under your color depth.
[OP]
Deal Addict
Jan 22, 2009
3393 posts
1201 upvotes
SizableSac wrote: I highly doubt that they would specifically gimp anything with DP 1.2 on purpose. Doesn't everything using DP use Display Stream Compression (DSC) these days? I still think it is an issue with your setup even though it was working before.

List of issues to check after reverting to system defaults:
Change all monitor settings (G83A needs to have DP 1.4 enabled specifically otherwise it is only using the 1.2 standard)
Monitor mode preventing specific color/res options?
Have you tried another DP cable?
What does your Display Specs say in Radeon Software? I also dont see pixel format under your color depth.
Thanks for the help!

Question: Could you let me know how to enable DP 1.4 on your G83A? Do you select it in the Input menu of OSD? I only have a single "DisplayPort" option display in the Input OSD. Probably due to my old GPU only support DP 1.2.

For my GP850, the setting I'm using are as follows:
Adaptive-Sync: Basic
HDR: OFF
Response Time: Fast
OSD shows 120hz by default.

And here is the complete screen shot of the default setting I have in Radeon display setting. Please note in my case pixel format only shows up for HDMI connection. pixel format option will disappear for DP.
850 1.JPG
850 2.JPG

And here is the default setting in Windows. As you can see, no 144hz:
390.JPG
Member
Nov 20, 2014
278 posts
95 upvotes
Ottawa, ON
braveblade wrote: Thanks for the help!
To enable DP 1.4 Should be under general, not inputs, not sure if its different on the new screen. All of my screen mode options still show 144 hz even when disabling DP 1.4
Image

You also dont have this option for some reason.
Image

My Windows settings shows the actual monitor name as well
Image

Also looking at your display specs according to Radeon Settings your max refresh rate of the monitor is 120hz which is why windows will also default to it. So there is something happening in your monitor to give you 120hz only. Are you using a straight DP to DP cable or are you using something else like a HDMI to DP dongle? Have you updated your Radeon Drivers to the latest ones? There are lots of things that can cause these issues, but its usually solvable.

This is all still going off the fact that you are sure that your older monitor works fine at 144hz and 10 bit.
[OP]
Deal Addict
Jan 22, 2009
3393 posts
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SizableSac wrote: To enable DP 1.4 Should be under general, not inputs, not sure if its different on the new screen. All of my screen mode options still show 144 hz even when disabling DP 1.4

You also dont have this option for some reason.

My Windows settings shows the actual monitor name as well

Also looking at your display specs according to Radeon Settings your max refresh rate of the monitor is 120hz which is why windows will also default to it. So there is something happening in your monitor to give you 120hz only. Are you using a straight DP to DP cable or are you using something else like a HDMI to DP dongle? Have you updated your Radeon Drivers to the latest ones? There are lots of things that can cause these issues, but its usually solvable.

This is all still going off the fact that you are sure that your older monitor works fine at 144hz and 10 bit.
Thanks man I really appreciate that you take time to help me!

I indeed found the DisplayPort under General, and it's default to 1.4. So everything is good here.
I'm using a DP to DP cable that comes with GP850. I tested the same cable with GL83A and Windows default it to 144hz at 10 bit. GP850 still defaults to 120hz at 10bit. I also updated both drivers for GP850 and Radeon.

At this point I give up. I can still use 144hz if I want to by adding it as a custom resolution, but at 8 bit color. My GPU is so old that I don't think I can push most of the games to 144hz anyway. The fact that I can enable 144hz as custom resolution means the monitor is not defective, just somewhere in my system/gpu is causing the issue. I can try to do the firmware update for GP850 but I'm afraid to brick the monitor.
Deal Fanatic
Feb 16, 2006
5056 posts
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Vancouver
I'm thinking about the ICC profiles provided for this monitor.

There have been issues in the past with v4 ICC profiles and people reverted or, using colorimeters, created their own ICC profiles saved to the ICC v2 standard.

Maybe there is something in there re 8bit vs 10bit bandwidth efficiencies.

It's a stretch but I have seen this being an issue in the content creation world.

.
[OP]
Deal Addict
Jan 22, 2009
3393 posts
1201 upvotes
zerod wrote: If you haven't tried a clean install (factory reset) of the graphics drivers, try that.
It should be a checkbox in the install options:
https://www.pcworld.com/article/3531288/if-youre-having-graphics-card-problems-try-a-clean-driver-install.html

If you disable 10-bit on the monitor, do you see the higher refresh rates?
Thank you!

Tried a clean install of GPU driver but still no luck.
Yeah I can use 144hz but only at 8 bit color. So it's a choice between 2560 X 1440 at 120hz and 10 bit, or 2560 X 1440 at 144hz and 8 bit.
Member
Feb 9, 2008
407 posts
329 upvotes
Vancouver, BC
Could possibly be a limitation of your graphics card's DP 1.2, as mentioned above.
That monitor is supposed to reach 165/180Hz, unless I'm looking at the wrong one.
Not sure why the old monitor works, unless you're not actually getting 10-bit despite what it says?

According to this chart, DP 1.2 can do 144Hz at 2560x1440, but that's 8-bit.
Makes sense that you're hitting the limit with 10-bit, which is why you're seeing 120.
[OP]
Deal Addict
Jan 22, 2009
3393 posts
1201 upvotes
zerod wrote: Could possibly be a limitation of your graphics card's DP 1.2, as mentioned above.
That monitor is supposed to reach 165/180Hz, unless I'm looking at the wrong one.
Not sure why the old monitor works, unless you're not actually getting 10-bit despite what it says?

According to this chart, DP 1.2 can do 144Hz at 2560x1440, but that's 8-bit.
Makes sense that you're hitting the limit with 10-bit, which is why you're seeing 120.
Thanks! Yeah I'm leaning towards GL83A showing 144hz at 10 bit is a bug. I found similar questions online that people were wondering why GL83A can hit 144hz and 10 bit at old gpu while the newer monitors cannot.

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