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Pixel Clock is a negative Value
12-25-2021, 07:38 PM
Post: #1
Pixel Clock is a negative Value
Hi. Recently my laptop's refresh rate causes it's screen to flicker at 60hz and 144hz. I have posted this issue on other forums and the answers i got was mainly pointing to the laptop's display cable. I have checked the laptop's edid and i have discovered that it's pixel clock is -287MHz for both 60 and 144hz refresh rates instead of the default 368MHz. So what may be the cause of the flickering problem a cable issue or the negative pixel clock? Thanks in advance.
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12-25-2021, 07:54 PM
Post: #2
RE: Pixel Clock is a negative Value
It's not possible for the pixel clock to be negative. Where are you seeing a negative pixel clock?
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12-25-2021, 08:47 PM
Post: #3
RE: Pixel Clock is a negative Value
(12-25-2021 07:54 PM)ToastyX Wrote:  It's not possible for the pixel clock to be negative. Where are you seeing a negative pixel clock?
I was able to view the laptop's edid using eldim edid viewer. It reads edid from windows registry.


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12-25-2021, 09:24 PM
Post: #4
RE: Pixel Clock is a negative Value
Well that's not correct. They probably used a signed 16-bit integer for the pixel clock, so it wrapped to a negative value after 327.67 MHz.

655.36 - 287.22 = 368.14 MHz

Use CRU to read the correct values.

Flickering is usually a signal-quality problem, so it's probably a cable or other physical issue.
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12-25-2021, 10:10 PM
Post: #5
RE: Pixel Clock is a negative Value
(12-25-2021 09:24 PM)ToastyX Wrote:  Well that's not correct. They probably used a signed 16-bit integer for the pixel clock, so it wrapped to a negative value after 327.67 MHz.

655.36 - 287.22 = 368.14 MHz

Use CRU to read the correct values.

Flickering is usually a signal-quality problem, so it's probably a cable or other physical issue.
Ok. Thanks. But it is somehow stable at 30hz refresh rate. I used your CRU to set it to 30hz. But after every 4-5 seconds dim lines appear on the screen. is it also due to a cable problem?
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12-26-2021, 04:45 PM
Post: #6
RE: Pixel Clock is a negative Value
30 Hz might be too low. Try 60 Hz with "Automatic (PC)" or "CVT-RB" timing. If it doesn't display that correctly, then it's likely the panel can only handle a fixed pixel clock since the default 60 Hz has increased blanking to match the pixel clock for 144 Hz.
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12-26-2021, 09:49 PM
Post: #7
RE: Pixel Clock is a negative Value
(12-26-2021 04:45 PM)ToastyX Wrote:  30 Hz might be too low. Try 60 Hz with "Automatic (PC)" or "CVT-RB" timing. If it doesn't display that correctly, then it's likely the panel can only handle a fixed pixel clock since the default 60 Hz has increased blanking to match the pixel clock for 144 Hz.
Ok. But, I have already tried those settings and the problem still persist. 30hz at 76Mhz pixel seems to be the only stable option. Guess it has go to the repairs then. Thanks for your time.
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