Nvidia driver 455.23.04 (beta?): lost 4K display

zebulon · 2020-10-06 09:19:51

I think this is solved, or at least we have an explanation from the Nvidia developer I was in contact with (and who has been fantastic at helping).

To connect to my TV I use a DP to HDMI cable from CableMatters. It turns out that my cable, which is a couple of years old, may be of Type 1, which supports max pixel clock up to 165MHZ (whereas Type 2 support up to 300 MHz). Therefore resolutions above 1920x1080 are rejected. Now why was it previously working in 4K with driver 450.66? Well, there was a bug in 450 and earlier drivers wouldn't respect these limits. That was fixed in 455, so now modes that require a pixel clock greater than what the cable is rated for will be rejected.

I have now 2 options:

Change my cable for one with a higher spec (e.g. DP 1.4 to HDMI 2.0)
Or it is possible to override the maximum pixel clock check by adding the following to the "Screen" section of the Xorg configuration file:
Option "ModeValidation" "NoMaxPClkCheck"
But that also means having to create my own modelines for the higher resolutions. Technically, I'll be exceeding the specified capabilities of my cable, so there's a risk of some instability, but since it was working fine with 450 it will probably be fine. That also means that CableMatters makes good quality cables that can handle higher specifications than the official ones.

Last edited by zebulon (2020-10-06 09:21:00)

seth · 2020-10-06 09:32:57

# 3840x2160 @ 60.000 Hz (CVT) field rate 59.981 Hz; hsync: 134.177 kHz; pclk: 712.75 MHz
Modeline "3840x2160_60.00" 712.75 3840 4152 4576 5312 2160 2163 2168 2237 -hsync +vsync

# 3840x2160 @ 60.000 Hz Reduced Blank (CVT) field rate 60.000 Hz; hsync: 133.320 kHz; pclk: 522.61 MHz
Modeline "3840x2160_60.00_rb2" 522.61 3840 3848 3880 3920 2160 2208 2216 2222 +hsync -vsync

There's no way to get 3840x2160 @ 60.000 anywhere near down to 300MHz (let alone 165)

# 1920x1080 @ 60.000 Hz (CVT) field rate 59.963 Hz; hsync: 67.158 kHz; pclk: 173.00 MHz
Modeline "1920x1080_60.00" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync

# 1920x1080 @ 60.000 Hz Reduced Blank (CVT) field rate 60.000 Hz; hsync: 66.660 kHz; pclk: 133.32 MHz
Modeline "1920x1080_60.00_rb2" 133.32 1920 1928 1960 2000 1080 1097 1105 1111 +hsync -vsync

The symbol rate is 125% ie. to make the required 712.75 MHz you'll need a cable that exceeds 712.75/1.25 = 570 which will only be matched by the 600MHz of "HDMI Premium High Speed" (yes, that shit is the official version tag - google it. There's no type1/2/3/whatever) cables.

340 MHz cables will get you that resolution at 24Hz & 30Hz only.

zebulon · 2020-10-06 10:17:11

seth wrote:

The symbol rate is 125% ie. to make the required 712.75 MHz you'll need a cable that exceeds 712.75/1.25 = 570 which will only be matched by the 600MHz of "HDMI Premium High Speed" (yes, that shit is the official version tag - google it. There's no type1/2/3/whatever) cables.
340 MHz cables will get you that resolution at 24Hz & 30Hz only.

Many thanks for all these precisions. My issue is that my graphics card has only DP output, and TV has only HDMI. So I have to either buy:

a DP to HDMI cable, I found two that have very high specs: https://www.amazon.de/-/en/Displayport- … =UTF8&th=1 or https://www.amazon.de/-/en/CSL-DisplayP … QHWNP&th=1 (this one is also certified HDCP 2.3
a good quality HDMI cable (some are certified 2.1, up to 8K, so future-proof) and an adapter. Unfortunately I am not sure about this second option. It looks difficult to source a high spec adapter and am concerned about it being the weakest link of the chain.

Any recommendation? Thanks a lot in advance.

Last edited by zebulon (2020-10-06 10:38:12)

seth · 2020-10-06 11:17:38

From the forum stats, HDMI adapters largely seem Chinese roulette - but you've unconditional RMA in Germany, so…

I'd rather go w/ an integrated adapter rather than an adapter where you need to plug an extra cable in, because the latter creates an additional obstacle (chance for the HDMI handshake to wet itself…) whereas the integrated ones an't bail on "yeah… your cable's probably shit".

nb. that the integrated adapters are unidirectional only as well (ie. you can't connect an HDMI output to a DP input) and that high frequencies (144Hz) are not specified for cables ("Ultra High Speed" has 120Hz support for up to 10k resolutions, but 144Hz is not specified - even if the datarate should allow that for eg. 4k)

zebulon · 2020-10-06 13:12:06

seth wrote:

From the forum stats, HDMI adapters largely seem Chinese roulette - but you've unconditional RMA in Germany, so…
I'd rather go w/ an integrated adapter rather than an adapter where you need to plug an extra cable in, because the latter creates an additional obstacle (chance for the HDMI handshake to wet itself…) whereas the integrated ones an't bail on "yeah… your cable's probably shit".
nb. that the integrated adapters are unidirectional only as well (ie. you can't connect an HDMI output to a DP input) and that high frequencies (144Hz) are not specified for cables ("Ultra High Speed" has 120Hz support for up to 10k resolutions, but 144Hz is not specified - even if the datarate should allow that for eg. 4k)

Thanks a lot for the advice. Yes I was also concerned by adding an adapter on top of a cable. Will do the roulette and see what happens

zebulon · 2020-10-12 07:38:02

seth wrote:

From the forum stats, HDMI adapters largely seem Chinese roulette - but you've unconditional RMA in Germany, so…

As a follow-up, I can only concur what you say. Although the cable I bought is certified 4K@60Hz (CSL - 4k DisplayPort to HDMI Cable - 1m - DP 1.4 - UHD 2160p - 3840 x 2160 @ 60 Hz - HDR - HDCP 2.3, Black) it is not able to display at this frequency, only 4K@30Hz. Furthermore, audio pass-through is also disfunctioning, sound crackling or being muted from time to time... Will go back to the supplier. Funny thing is that my old "Cable Matters" cable is still able to display 4K@60Hz with the old driver, although it is not even 4K certified. Cable is thicker, maybe that is an element, although electronics are important. That said there is a slight bit of colour bleeding on the edge of characters at this frequency, but you really need to be close to the screen to realise.

Curiously, the new cable is detected on port DP-0, whereas my old cable is detected on DP-1, despite being connected on the same physical sockets! This happens with whatever display driver. There are really bizarre things with those cables.

zebulon · 2020-10-15 12:01:17

I bought a second cable, where all reviews were stellar (4K 60Hz supported): https://www.amazon.de/-/en/gp/product/B … UTF8&psc=1 and still no 60 Hz, image is completely garbled. Quality control is really lacking, and thankfully in the EU they can return to the supplier with no questions asked.

But I just realised that out of the 4 exit ports on the graphics card one is an HDMI! So I used an (old) HDMI cable and was able to reach 3840x2160 @ 60 Hz with it.

Strangely it is very easy to source good quality DP -> DP v1.4 or HDMI -> HDMI v2.1 cables that are rated to up to 8K@60Hz (and thus would guarantee 4K at very high refresh rates). However, finding a good DP -> HDMI adapter or cable is extremely difficult, unreliable and as you mentioned, a lottery.

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#26 2020-10-06 09:19:51

Re: Nvidia driver 455.23.04 (beta?): lost 4K display

#27 2020-10-06 09:32:57

Re: Nvidia driver 455.23.04 (beta?): lost 4K display

#28 2020-10-06 10:17:11

Re: Nvidia driver 455.23.04 (beta?): lost 4K display

#29 2020-10-06 11:17:38

Re: Nvidia driver 455.23.04 (beta?): lost 4K display

#30 2020-10-06 13:12:06

Re: Nvidia driver 455.23.04 (beta?): lost 4K display

#31 2020-10-12 07:38:02

Re: Nvidia driver 455.23.04 (beta?): lost 4K display

#32 2020-10-15 12:01:17

Re: Nvidia driver 455.23.04 (beta?): lost 4K display

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