Custom Resolution Utility (CRU)

[ToastyX]

(Today 12:56 AM)marcgii Wrote:  I asked Claude to analyze my monitor EDID info and why I can't achieve the rated refresh rate (5k180) even though DSC clearly works on both HDMI and DP1.4. The explanation it gave of Samsung screwed up the EDID sounds plausible. But can anyone here confirm it is likely an EDID problem? The numbers it cites here are correct.

Quote:Your monitor's own Display Range Limits descriptor in the base EDID block declares a max pixel clock of only 2550 MHz. But the actual 180Hz timing in the DisplayID block needs 2932.5 MHz. The monitor is contradicting itself — one part of its EDID says "I support up to 2550MHz," and another part lists a timing that needs 2932.5MHz. There's also a horizontal frequency mismatch (range limits say 510kHz flat, but 180Hz needs 532.8kHz — over that too).
This is precisely the kind of internal EDID inconsistency that makes a driver throw out the higher mode: Nvidia's driver reads the Range Limits descriptor as the monitor's own stated ceiling, sees the DisplayID 180Hz timing exceeds it, and drops it as invalid — while 120Hz (1978MHz, comfortably under 2550MHz) passes cleanly and gets exposed. That lines up exactly with what you're seeing: 120 works, 180 doesn't, on both DP and HDMI, because this is an EDID-side defect, not a link-bandwidth one.

The range limits descriptor is old and can't go higher than 2550 MHz pixel clock or 510 Hz/kHz, so those are the maximum values. NVIDIA's driver doesn't listen to the max pixel clock or horizontal range anyway, only the refresh rate range for adaptive sync.

The real issue is it's a GPU limitation. You need a 5000-series GPU to get 5120x2880 @ 165/180 Hz. Samsung doesn't seem to specify this anywhere, but the ASUS XG27JCG also supports 5120x2880 @ 180 Hz, and they mention a 5000-series GPU is required for 180 Hz.

I don't know what the limit for 4000-series GPUs is, but I would assume it would be 2x the single-head limit, so 2700 MHz. In theory, you could squeeze in 5120x2880 @ 165 Hz with reduced blanking, but not 180 Hz without very tight blanking intervals. Unfortunately, NVIDIA's driver won't let you experiment because it doesn't support custom resolutions or EDID overrides when using two heads for bandwidth.