Green lines

[Antinomy9]

Hey ive got a LG 25UM58-P its advertised as a 75 hz monitor but out of the box its on 60 hz. i oced it to 75hz a couple of months ago and had faced no problem. But today after some cable management work, ( plugging and unplugging both hdmi and power) some flashing green horizontal lines appeared. Noticed them on videos specifically. After deleting the custom resolution and putting on the default 1080p res from nvidia control panel under the PC text, the lines disappeared . i guess it was the oc that caused them but what else could have been?

[tire]

maybe artifacting on the gpu

[-rascal-]

On 3/22/2021 at 4:09 PM, Antinomy9 said:

Hey ive got a LG 25UM58-P its advertised as a 75 hz monitor but out of the box its on 60 hz. i oced it to 75hz a couple of months ago and had faced no problem. But today after some cable management work, ( plugging and unplugging both hdmi and power) some flashing green horizontal lines appeared. Noticed them on videos specifically. After deleting the custom resolution and putting on the default 1080p res from nvidia control panel under the PC text, the lines disappeared . i guess it was the oc that caused them but what else could have been?

 

It could be the overclock causing the issues.

This monitor shouldn't have been advertised as a "75 Hz" monitor, because it can't run native resolution with 75 Hz.

 

It can only do 75 Hz with VERY specific resolutions...

• 640 x 480
• 800 x 600
• 1024 x 768
• 1280 x 1024

https://www.lg.com/ca_en/support/product/lg-25UM58-P

 

[mariushm]

That table is about ANALOGUE (VGA) compatibility, what resolutions the analogue to digital converter part of the chip supports.

Because you may connect the monitor to all kinds of devices, not just computers, the monitor has to support a bunch of refresh rates and resolutions and convert them internally to something it can put on the lcd panel.

Besides those resolutions, the monitor probably supports other resolutions,  like let's say 512x256 (super nintendo I think) and other resolutions.

In addition to just resolutions, some of the original VGA and SVGA resolutions defaulted to refresh rates higher than 60 Hz, like let's say 72 Hz or 75 Hz.

 

The chip inside the monitor converts  whatever frames it receives from the vga connector, does , scaling, pan and scan if needed, and then the digital image is converted into the format the LCD panel supports  BUT the actual LCD panel is not capable of more than 60 Hz.

So the chip simply accepts 75 Hz (75 fps) but only sends 60 out of those 75 frames further to update the information on the LCD panel.

 

There's also a problem... because you send 75 frames per second instead of 60 through the vga cable, there's more information moving through the cable, which means every pixel color has a weaker signal and a smaller amount of time on the cable, and this means "electric noise" from outside the cable can affect the quality of the signal.

 

If you try to go with more than 60 hz on your hdmi cable, it's basically oveclocking your monitor in a way.