T420s Optimus Quad digital monitor output problem

I purchased a Thinkpad T420s with Optimus graphics along with a Mini Dock Plus Series 3 (4338-10U) to replace my triple monitor desktop setup. So far I’ve been unable to replicate Lenovo’s quad digital monitor setup described in the following documentation:

NVIDIA Optimus - ThinkPad Multiple Monitor Configurations

Technical Brief - Thinkpad Multiple Monitor Configurations Using nVidia OPTIMUS Technology

I’m trying to connect three Dell U2410’s (1920x1200) in the following fashion:

• Thinkpad Display (1600x900)
• Monitor 1 – DisplayPort (Thinkpad T420s) (1920x1200)
• Monitor 2 – DVI1/DP1 (Dock) (1920x1200)
• Monitor 3 – DVI2/DP2 (Dock) (1920x1200)

According to the documentation above, this configuration should work. The problem I’m running into is the nVidia NVS 4200 controls all the digital outputs (DVI & Displayport) and will only allow two displays. The Intel IGP controls the T420s display and the VGA outputs. I am able to get the setup running using the VGA output in place of the DVI output on the dock, but this is not an optimal solution.



According to the latest Readme.txt for the Optimus drivers:

NVIDIA Optimus Technology

…

DISPLAY TOPOLOGY

Since Optimus Technology has the ability to use two display adapters, some
display monitors (or displays) are assigned to specific adapter. Below
describes which display adapter controls the display connector for a certain
display monitor.


ThinkPad T420, T420i, T420s, T420si, T520, T520i
NVIDIA NVS 4200M
- Computer's DisplayPort connector
- Docking Station's DVI connector(s) or DisplayPort connector(s)

Intel HD Graphics Family
- (Computer's LCD)
- Computer's analog VGA connector
- Docking Station's analog VGA connector
​

So if the nVidia NVS 4200M controls all the digital outputs on the Thinkpad and dock, but only supports two displays, how can one use a quad display setup as described in Lenovo’s documentation?

So far I have been unable to get an answer from Lenovo Tech Support, which I have spent more time educating them on what their product should be capable of.

Latest BIOS (1.30)
Latest Optimus Drivers (8.17.12.7593)

Any help would be greatly appreciated.

 

In my case I had no problems driving four external monitors. However, I used different connections. On the dock I used VGA, DP1 and DVI2. I used the DisplayPort from the T420s using a DP->DVI adaptor for LCD panel number 4.

The LCD panels all used were Dell. 2x24", 27, and a 20".

The notebook lid was down and the T420s LCD panel was not used.

 

Thanks for the reply, did you use the nVidia console or Windows display properties when you were configuring your displays? If you used the nVidia console, did it not limit you to only two displays or did it allow you to pick three from the NVS 4200 section? I'm wondering if my case is the exception or if there just isn't anybody using the T420s in this type of configuration, you and I excluded. I would like to attach three external monitors using the docks DP1/DVI1 & DP2/DVI2, along with the Thinkpad's DP with the thinkpad screen closed, but this seems impossible.

 

I used the Windows 7 display properties, not the NVIDIA control panel.

 

Are you running the latest BIOS and Optimus drivers from Lenovo? Any chance you could post a screenshot of your nVidia control panel similar to mine? I'm completely stumped as to why I can't get this to work.