Custom Resolution Utility (CRU)

[ToastyX]

(11-03-2024 04:44 AM)amak Wrote:  The monitor doesn't appear in the list of displays...

I don't want to take up too much of your time, but one more thing of note: when I use a DVI cable instead, with a DVI-to-DP adapter, I think a valid EDID does go through, as I can see the monitor name and correct presets in CRU (the only issue there is no analog output to the monitor with that cable/adapter).

Does this narrow this down to a cable/adapter issue, and if so, would a hardware EDID emulator solve the issue?

It could still be the monitor because monitors often have separate EDIDs for each port, so the VGA D-sub port might have a corrupted EDID, while the DVI-A port might not. Since DVI-A is basically just VGA with a different plug, if you happen to have a passive DVI to VGA adapter, you can try DisplayPort to VGA adapter > VGA cable > VGA to DVI-A. If that works, then the EDID is probably corrupted on the monitor's VGA port, which tends to happen to old monitors sometimes when a bit flips in the monitor's EDID EEPROM.

Other options:

1. Use Windows 10, which will allow CRU to work with monitors that don't have a valid EDID.

2. Get a hardware EDID emulator. DisplayPort emulators aren't common and tend to be expensive, but if the adapter passes through the EDID, you can try a cheaper VGA EDID emulator instead. Then you should be able to use CRU with Windows 11. If the emulator is programmable, you could program the EDID directly to the emulator, but programmable ones tend to be more expensive. Edit: A VGA EDID emulator should work if the problem is the monitor or the cable but not if there's an issue with the adapter. A DisplayPort EDID emulator should work for all cases since it comes before the adapter.

3. Fix the EDID on the monitor. The problem is many monitors have the EDID write-protected, although some monitors have a way to disable the write protection through the service menu. I don't know if the IBM C220p is write-protected or if there's a way to disable the write protection. If it's not write-protected, you'll need a video card with a direct VGA connection. Then you can use my EDID/DisplayID Writer if it's an AMD card, or you can use Linux tools such as edid-rw to write the proper EDID.

[dotcomma]

Hello,
I'm trying to set custom max refresh rate on my monitor to be lower than native, but it does not accept it and shows that display resolution is not supported, any idea/tip what can I try please?

My monitor is Samsung OLED G8 with native resolution 3440x1440 at max refresh rate 175 Hz, VRR range is 48-175 (Gsync compatible).
Other than 175Hz, monitor also natively supports 60hz, 100hz and 120Hz resolutions.
I have Nvidia 4080 GPU and using DP connection with DSC, EDID override is accepted and luckily works for me on current Nvidia drivers.

What I tried is to edit Detailed Resolution in DP extension block and change the original 175Hz resolution to 150Hz, but keep the original pixel clock. Unfortunately it does not work, is it possible that VRR monitor is locked to some fixed Max refresh rates? If I try 100 or 120 Hz then it works, but only these. I would expect that if its VRR range is 48-175 it would accept native resolution with any refresh rate withing that range, especially if pixel clock is the same.

The reason for doing this is VRR flicker mitigation where fps limiters don't work.

[amak]

(11-03-2024 02:05 PM)ToastyX Wrote:  

(11-03-2024 04:44 AM)amak Wrote:  The monitor doesn't appear in the list of displays...

I don't want to take up too much of your time, but one more thing of note: when I use a DVI cable instead, with a DVI-to-DP adapter, I think a valid EDID does go through, as I can see the monitor name and correct presets in CRU (the only issue there is no analog output to the monitor with that cable/adapter).

Does this narrow this down to a cable/adapter issue, and if so, would a hardware EDID emulator solve the issue?

It could still be the monitor because monitors often have separate EDIDs for each port, so the VGA D-sub port might have a corrupted EDID, while the DVI-A port might not. Since DVI-A is basically just VGA with a different plug, if you happen to have a passive DVI to VGA adapter, you can try DisplayPort to VGA adapter > VGA cable > VGA to DVI-A. If that works, then the EDID is probably corrupted on the monitor's VGA port, which tends to happen to old monitors sometimes when a bit flips in the monitor's EDID EEPROM.

Other options:

1. Use Windows 10, which will allow CRU to work with monitors that don't have a valid EDID.

2. Get a hardware EDID emulator. DisplayPort emulators aren't common and tend to be expensive, but if the adapter passes through the EDID, you can try a cheaper VGA EDID emulator instead. Then you should be able to use CRU with Windows 11. If the emulator is programmable, you could program the EDID directly to the emulator, but programmable ones tend to be more expensive. Edit: A VGA EDID emulator should work if the problem is the monitor or the cable but not if there's an issue with the adapter. A DisplayPort EDID emulator should work for all cases since it comes before the adapter.

3. Fix the EDID on the monitor. The problem is many monitors have the EDID write-protected, although some monitors have a way to disable the write protection through the service menu. I don't know if the IBM C220p is write-protected or if there's a way to disable the write protection. If it's not write-protected, you'll need a video card with a direct VGA connection. Then you can use my EDID/DisplayID Writer if it's an AMD card, or you can use Linux tools such as edid-rw to write the proper EDID.

Spot on!! Corrupted EDID on the VGA port it seems. A DVI to VGA cable, with the same VGA-to-DP adapter, fixed the EDID issue. The monitor now appears in settings/CRU with the correct name, with all factory display modes filled out in CRU.

I still can't get custom resolutions to appear in settings though :(

Here's the output from both edid-tests we've used (identical), I hope it can pinpoint the issue:

DISPLAY\IBM1A4F\7&176FD83E&0&UID260 (active):
00 FF FF FF FF FF FF 00 24 4D 4F 1A 01 01 01 01
1B 0E 01 03 6E 29 1E AC EB 9C 68 A0 57 4A 9B 26
12 48 4C A4 43 00 D1 59 C1 59 81 99 E1 4F 61 59
45 59 A9 4F 31 59 A6 59 40 30 62 B0 32 40 40 C0
13 00 88 26 11 00 00 1E 00 00 00 FF 00 32 34 2D
42 38 39 32 39 0A 20 20 20 20 00 00 00 FC 00 49
42 4D 20 43 32 32 30 50 20 43 52 54 00 00 00 FD
00 32 A0 1E 82 25 00 0A 20 20 20 20 20 20 00 15

Again, much appreciation for all the help so far.