Three external displays at the same time not working

[SteveE]

I am trying to connect three displays. I can enable any two of the three displays at one time, but never three at one time.

- The configuration is a Dell PC with three external displays (details below).
- All displays are using Displayport connections via a Displayport splitter with MST.
- At power up, the Windows startup icon appears on all three displays.
- All displays get recognised and shown in the Intel Graphics Command Centre, although the 3rd one is disabled (see 1st image). Clicking Enable has no effect.
- Two displays are shown in the Intel HD Graphics Control Panel. The third one appears in the drop down selections, where I can sucessfully switch between them all (see 2nd image)
- Windows does show the third monitor within Settings, but as a small image (see 3rd image).
- I have disabled/enabled the drivers for the display adapter and each monitor without effect.
- I have tried every combination of powering down/up for the devices without effect.
- I have not updated drivers with any from Intel. I am using the Windows provided ones.
- I have tried a different DP splitter without effect.

My configuration is:
- PC is Dell Optiplex 3020M, i5-4590T @ 2.00Ghz, Windows 10 Pro 22H2
- Monitor 1 Samsung C32F391
- Monitor 2 Dell U2412M
- Monitor 3 Dell U2412M
- Display Adapter: Intel HD Graphics 4600

The PC supports 3 monitors:
https://ark.intel.com/content/www/us/en/ark/products/80815/intel-core-i54590-processor-6m-cache-up-to-3-70-ghz.html

A 3 monitor configuration is suported by the Intel HD Graphics 4600 card:
https://www.intel.com/content/www/us/en/support/articles/000025673/graphics.html

I have reviewed various posts on similar issues, but have not been able to solve the problem.

Is there any advice or further diagnosis I can undertake?

Regards
Steve

[AlHill]

If your device is a laptop, the laptop screen counts as one display.

Doc (not an Intel employee or contractor)
[Maybe Windows 12 will be better]

[SteveE]

It's for a PC, so I'm just looking for three external displays to work.

Regards
Steve

[n_scott_pearson]

[Aside: Please don't use the word 'splitter'; it only applies to duplicating displays, which is not what you want.]

How do you have these monitors connected? Is this a 3-port MST Hub? What is the vendor and model number for this MST Hub?

I might suggest using the MST Hub with the two U2412M monitors, connecting them via the DP port, and the C32F391 separately, connected via the VGA port. 

Hope this helps,

...S

[SteveE]

Yes. They are connected via a 3 port MST hub. I have tried these two without success:

StarTech.com 3-Port Multi Monitor Adapter
https://www.amazon.co.uk/gp/product/B00JLRBC7S

8K Displayport Multi-Monitor Adapter Splitter
https://www.amazon.co.uk/gp/product/B09LLL3QSZ

I have changed the video connection from DP to VGA (direct from the PC's VGA port) for one of the U2412M monitors, with the DP cable unplugged. (Doing that for the C32F391 is a bit tricky cabling wise.) The monitor works perfectly well but behaves in the same way as when it is connected via DP. i.e.  I can enable any two of the three displays at one time, but never three at one time.

This is all very odd as it should work according to all the specs and documentation. I do find it suspicous that all three display the Windows icon at power startup, but never afterwards.

Regards
Steve

[n_scott_pearson]

I am afraid I don't have the hardware to test this just now (my MST Hub is USB-C-based, not pure DP). If you can wait, I have one on order (to support my 2x4 KVM) and will be able to investigate when it arrives on Monday.

...S

[SteveE]

I've been trying everything for 9 months to get this working so I'm in no hurry. Anything you can tell me would be appreciated.

Regards
Steve

[SteveE]

For what it's worth, I've given up trying to solve this problem. I guess three displays will have to wait until my PC hardware needs replacement.

For anyone reading this who is trying the same thing with a Dell Optiplex 3020M with an Intel Graphics card (or similar), beware that while the formal specs may say three displays work, they may not.

[Druners]

Hi Steve, you can try doing what solved it for me.  I switched the secondary monitors to DP 1.2 instead of 1.4 and it allowed me to have all 3 monitors on.

[SteveE]

Hi Druners

Thank you for the suggestion. However I cannot find how to change the DP version from 1.4 to 1.2 - from what I can see, the option is not within Windows, the Intel Graphics Command utility, the Dell BIOS, or via the on screen display on the monitors.

One of the DP hubs (StarTech.com 3-Port Multi Monitor Adapter https://www.amazon.co.uk/gp/product/B00JLRBC7S) is limited to DP 1.2 so I'm guessing that would apply the lower version anyway.