Daisy Chain 4 Dell U2719D Ultra Sharp Monitors

Question

Hi Everyone.

I have a Dell Precision 7750 laptop and i connected 4 x Dell U2719D monitors in a daisy chain using a StarTechcom CDP2DP14B type C to DP converter. All 4 monitors worked for about a month then all stopped working. We have established that there is nothing wrong with the laptop, adaptor and monitors. Windows was corrupt. we re-installed and the monitors started to work but only 2. We disabled a setting in the bios which made 3 work but the Nvidia graphics say it only supports 4 monitors which includes the laptop monitor. They all worked before so am i missing something?

I have read that mst must be enabled but these monitors do not go into any setup menu like that. They seem to detect everything themselves. When i look at the guide online it shows a menu which is not available on these monitors. Like i said the automatically worked when we connected the first time.

TIA

jphughan · Accepted Answer

@WozzaMac If you have switchable graphics still enabled, the Intel GPU will be running the internal display, so it wouldn't count toward the NVIDIA GPU limit. But enabling "Graphics special mode" or whatever they might be calling it now would allow the NVIDIA GPU to control all external displays. In that setup, you'd be able to support five total displays if one is the built-in display. However, if your setup worked before, then I'm not sure why you had to change a BIOS setting after a Windows reinstall to achieve that setup again, unless perhaps somebody reset the BIOS to factory defaults during the Windows reinstall.

However, a daisy chain of four QHD displays may not be a great idea anyway because if the daisy chain is running in DisplayPort 1.2/HBR2 mode, the only way you'd have enough bandwidth along the daisy chain to run quad QHD is if all displays are running at 30 Hz rather than the standard 60, which is not a great experience. If you were using DisplayPort 1.4/HBR3, you would have enough bandwidth for quad QHD 60 Hz, but I don't know if that's the case, and I've also never had success running long daisy chains even in scenarios where bandwidth isn't a concern.

Just as a test, what happens if you run a two-display daisy chain from your USB-C port and then set up a separate two-display daisy chain using a Mini-DisplayPort to DisplayPort cable to the first display in that chain?

WozzaMac · Answer

Thank you for your response.  I will try see how i enable that 'special mode' and revert.

WozzaMac · Answer

Hi There

So i enabled switchable graphics mode in the bios again and there was another option to tick next to it which i did. There's no other options to select. I then added the last monitor in the Nvidia control panel and everything worked. Thanks for your help.

jphughan · Answer

@WozzaMac  Great news! Thanks for reporting back, and glad to hear you’re good to go.

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Daisy Chain 4 Dell U2719D Ultra Sharp Monitors

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