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PC Graphics

enzo873927
Journeyman III

Minimum resolution and maximum pixel clock

My RX 7900 XT is connected to three monitors: two typical LCD monitors which work fine, and a CRT monitor via a DisplayPort-to-VGA converter, which has two issues.

  • Issue 1: The minimum resolution is arbitrarily set to 400x400. I can't set, say, 399x400 (or 399 x anything), nor can I set 400x399
  • Issue 2: The maximum pixel clock is set to 180 MHz. I can set 1600x1200 at 60Hz, but not at 75Hz

The first issue is problematic for playing "retro" or pixelated games at their native resolution with scanlines, usually at resolutions around 240x360. The second issue makes high-resolution display modes impossible to use.

These issues affect the custom-resolution panel in the Adrenalin software, such that these custom resolutions are rejected ("The custom resolution settings are not compatible with this display. Reconfigure your settings and try again."), but they also cause display modes built into the monitor's EDID to not appear (even in "Advanced display settings > Display adapter properties").

My system is a dual-boot, and neither of these issues exist (with the exact same hardware) in a Linux environment. Also, I used to have a GPU from a different company -- it was also OK, in both OSes. Therefore, the GPU, VGA converter, cables, and monitor are all OK, as well as Windows 10 itself. The problem therefore must be the AMD Windows 10 drivers.

Because all the cutoff thresholds are very neat, round numbers (400, 400, and 180), I suspect that these limits were deliberately added to the driver software. Is there any way to bypass these limits?

2 Replies
Kirillmiha0914
Journeyman III

I have same problem with 180 MHz limit on my RX 6600 XT, i'm using NEC multisync 95f and hp as615aa dp-vga stdp3100-based adapter. What adapter and monitor you using?

About EDID, my adapter transmits data wrong, maybe your's too, my monitor EDID hex code starting from 43 instead of 00, i read it using EDWriter, it said that edid corrupted ant offered to fix it, i saved both as bin files and opened it with edid decoder online, got "error-couldn't open" with non-fixed file, fixed one decoded pretty normal. I found some instructions for replacing data from monitor by custom edid file, didn't tried it yet but hope this method can fix correct monitor detection at leastd

Upd. Something wrong with monitor, changed it by LG Flatron F720p, list of affordable resolutions and monitor name detected correctly, but it didn't solve problem with 180 MHz limit, monitor can show 1920x1440@60Hz on DMT timings, but it's still impossible to set smth higher than 1600x1200@60Hz (65Hz on DMT, 66HZ on CVT, custom resolution) 

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Kirillmiha0914
Journeyman III

Maybe your converter just sucks. Yesterday i bought dp-vga dongle based on rtd2166, EDID detected properly on both my CRTs, default resolution (1280х1024, 85hz) sets automatically, and now it's able to set 1920x1440 on 60 Hz via display settings, tried some manual resolution settings via Custom Resolutions utility, i recommend to use it cause amd driver software still doesn't allow me to overlimit 180 mhz, cru may need amd limit unlock patch, link will be on CRU page in description

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