Increasing video cable length

[sacentre]

Dear All

I'm using a Dell U2711 monitor at its max res of 2560x1440 on an ATI Radeon R9-270X card.

It works fine on the Dell supplied, 2 metre DVI-D dual link cable but I need to increase the video cable length to at least 3 meters.

No cable I've tried works correctly. Can anyone please tell me what I'm missing.

1. I've tried 6 different DVI-D dual link cables, all 3 meters long. None of them can support 2560x1440.

2. I read that HDMI v1.4 cables should support the max res of the monitor but found that the 3 meter cable I bought (claiming to be v1.4 on the pack) automatically lowered the res to 1680x1050.

3. Finally, I tried the Dell supplied 2 meter, DisplayPort cable (prior to shopping for a longer one and this worked fine until the monitor started blanking to black for a few seconds every 10-15 mins (all screen saver or power saving settings are unchecked).

I find this situation very frustrating. Can anyone tell me what I have to do to run this monitor at max res on any kind of 3 meter cable?

Thanks for reading

Trevor

[ToastyX]

That's weird. 3 meter DVI cables should be able to handle 2560x1440. Are you sure they were dual-link DVI cables?

2560x1440 won't work with HDMI unless you patch the driver and add a custom resolution:

https://www.monitortests.com/forum/Threa...ck-Patcher
https://www.monitortests.com/forum/Threa...tility-CRU

You shouldn't have any trouble with 3 meter DVI cables or 2 meter DisplayPort cables. The monitor might be defective.

The software setting I can think of that might help is make sure "Alternate DVI operational mode" is enabled in CCC.

[sacentre]

(01-12-2014 06:13 PM)ToastyX Wrote:  That's weird. 3 meter DVI cables should be able to handle 2560x1440. Are you sure they were dual-link DVI cables?

2560x1440 won't work with HDMI unless you patch the driver and add a custom resolution:

https://www.monitortests.com/forum/Threa...ck-Patcher
https://www.monitortests.com/forum/Threa...tility-CRU

You shouldn't have any trouble with 3 meter DVI cables or 2 meter DisplayPort cables. The monitor might be defective.

The software setting I can think of that might help is make sure "Alternate DVI operational mode" is enabled in CCC.

You'd think an extra metre wouldn't be that hard for a DVI-D cable but as I said, I've tried 6 of different ones now and the result is the same. They were all Dual Link cables according to the plugs but with most of this stuff originating in the far East, who knows what's inside or what cheap conductors have been used?

I also tried adding a custom res with the CRU using an HDMI cable but couldn't get it to work. Basically nothing happened.

Sorry to be dim, but where is that setting in the CCC?
Thanks for listening.

Trevor

[ToastyX]

(01-13-2014 03:01 PM)sacentre Wrote:  I also tried adding a custom res with the CRU using an HDMI cable but couldn't get it to work. Basically nothing happened.

Did you patch the driver? You might have to disable the extension block as well if there happens to be a limit set in there.

(01-13-2014 03:01 PM)sacentre Wrote:  Sorry to be dim, but where is that setting in the CCC?

It's under "My Digital Flat-Panels" -> "Properties" below the GPU scaling options.

[sacentre]

Thanks again, but I'm still not able to make CRU change the res. The max res I can see is still 1920x1080 using the HDMI cable and I now have a 1" black margin all around the screen image. After adding the custom res 2560x1440, are there any other steps after clicking on "OK"?

I know I'm the weak link in all this.

[ToastyX]

Make sure 2560x1440 is listed as the first detailed resolution. Use the arrow buttons to move them around. The only other step is to reboot. Usually patching the driver and disabling the extension block in CRU is enough to make the resolution available.

If that isn't working, enable the extension block and import this file: https://www.monitortests.com/hdmi.dat

You might not need the patch if you do that.

[sacentre]

ToastX

Many thanks for your advice and patience. I finally realised (and I can imagine your eyes rolling) that I needed to edit the refresh rate setting in CRU to get an HDMI cable to work at 2560x1440. In the manual for my Gigabyte motherboard, it states that the onboard HDMI port can support a max res of 4096x2160@24Hz so I edited the refresh rate on the CRU to 24Hz and it works just fine. (I also read the specs for the new Dell P2815Q which says that 4K res is only supported at 24Hz so this got me thinking).

So, next I tried upping the refresh rate in steps of 5Hz at a time and have found that I can go up to 55Hz before the display res automatically drops back. It won't work at 59 or 60Hz.

Does this sound right or is CRU or the driver or whatever simply ignoring anything above 24Hz? The display performance seems quick enough even running HD movies so I'm happy with that.

Should I also change any other settings like the ones you suggest below or will they make no difference now?

Many thanks once again.

Trevor

(01-21-2014 01:40 AM)ToastyX Wrote:  Make sure 2560x1440 is listed as the first detailed resolution. Use the arrow buttons to move them around. The only other step is to reboot. Usually patching the driver and disabling the extension block in CRU is enough to make the resolution available.

If that isn't working, enable the extension block and import this file: https://www.monitortests.com/hdmi.dat

You might not need the patch if you do that.

[ToastyX]

The driver is ignoring the resolution. It seems like you're hitting a 225 MHz pixel clock limit, possibly defined in the extension block. You should be able to get 60 Hz if you enable the extension block and import that file.

[sacentre]

Thank you once again.

The "Include extension block" box is checked. I have also downloaded the hdmi.dat file. Apologies, I'm afraid I have to ask now where I'm supposed to copy it to.

(01-28-2014 03:37 PM)ToastyX Wrote:  The driver is ignoring the resolution. It seems like you're hitting a 225 MHz pixel clock limit, possibly defined in the extension block. You should be able to get 60 Hz if you enable the extension block and import that file.

[ToastyX]

Click the "Import..." button to import the file. You don't need the file anymore after it's imported.