Min spec to run 2 x 4K monitors?

[Kiwi79]

Hi PH'ers,

Is there a minimum spec to run 2 x 27inch 4k monitors side by side from 1 laptop. My work laptop is a somewhat ageing IBM ThinkPad but it does have 16GB RAM and once connected to it's dock 2 x Display port outputs are available.

What's the crucial thing? Graphics card spec?

Spec is I5-6300U 2.4GHZ
Graphics apparently Intel HDGraphics 520

Thanks


Simon

[xeny]

Depends quite a bit on the dock. Have you tried googling the model of the doc and "spec" ?

[robbieduncan]

What sort of work are you doing? I use a DisplayLink dock (DisplayLink supply the tech to many manufacturers). It connects to my laptops over USB C and has 2x4k screens and a bunch of USB peripherals attached

As everything is over one USB C connection the screens are never going to support gaming (and I’m sure there is compression so probably not graphics or video work). But for development and office type work its ideal

[QuartzDad]

Having been through this recently the answer is it can get complex.

For instance are you happy with 4k with just 30Hz refresh rates? Some can't see a difference, some state anything less than 60Hz is unusable.

Are you fussed about the clean one cable look or are you happy with running one screen via a dock and one direct from the laptop?

As someone else said, what you can display is to a large degree driven by the dock specs. Look at the Lenovo dock output capabilities for examples https://support.lenovo.com/gb/en/solutions/pd02962...

I've got a three year old ThinkPad, a ThinkPad dock and a pile of not-quite-right cable purchases to eventually work out that to drive 2 x 4K @ 60Hz and have just one dock cable for my particular hardware combo required one TB to DP cable and one DP to DP cable.

[sjg]

Which thinkpad? Spec sounds similar to my T470S and the only way I could do a single 4k at 60hz was using a USB-C to HDMI adaptor, the onboard HDMI wouldn’t do it.

[walamai]

robbieduncan said:

What sort of work are you doing? I use a DisplayLink dock (DisplayLink supply the tech to many manufacturers). It connects to my laptops over USB C and has 2x4k screens and a bunch of USB peripherals attached

As everything is over one USB C connection the screens are never going to support gaming (and I’m sure there is compression so probably not graphics or video work). But for development and office type work its ideal

The are (roughly speaking) two types of dock;

DisplayLink
These are designed for backwards compatibility and will work with just about any old computer (no matter if the computer itself has HDMI or DisplayPort outputs). The dock itself has video hardware in it, and the computer will process the video data so that it can pass it to the dock over USB. Depending on your computer, it may be the CPU or Graphics card (or both) doing this work. In any case, the CPU will have a bit of 'overhead' to process the video data and send it to the dock over USB.

The spec of the dock itself will determine what displays you can connect to it. With your laptop, if the dock you have supports 2x4K then you'll be fine for 'office productivity' stuff.


USB-C 'Alt Mode'
This is a bit simpler. The 'Alt (alternate) Mode' refers to the fact that Display Port signal is being sent over the USB-C cable.ie; it's 'alternative' to the USB protocol.
This basically works exactly like having a DisplayPort cable plugged straight from your laptop to the displays. (Constrained only by the max bandwidth of USB.) Your laptop GPU does the graphics processing without the DisplayLink CPU virtualisation overheads.
Again though, just check the spec of the dock itself to see if it will do 2 x 4K. If the dock supports it, then your laptop will be fine.


Confusingly, both docks can use a USB-C cable to connect to the laptop. (So both will provide power as will as display signals etc). You have to read the tech spec fine print to see which is which.


TLDR; You laptop will do 2 x 4K, check the specs of your dock to see what is supported. If buying a dock, I'd recommend USB-C Alt Mode over DisplayLink, all things being equal.

[Kiwi79]

Thanks for the replies. I can see this a bit more complex than I thought. The Laptop is a Thinkpad T460 and the Dock not entirely sure but it's IBM of similar age looks like a Thinkpad Pro dock on google image search

[xeny]

If you look in device manager or on the bottom of the dock is there perhaps a model number?

[walamai]

Sorry yeah, I may have overcomplicated things!

Your laptop will be fine, it's down to the dock. Have a look underneath or on the back, it should have a model number somewhere.

[xeny]

walamai said:

Sorry yeah, I may have overcomplicated things!
.

It's the best explanation of alt mode vs DisplayLink I've seen here.

Wish there were a way to link to individual posts so I could easily refer to it in the future, and also wave it at part of our parent org's IT purchasing department, who seem convinced DisplayLink docks are the solution for all kinds of user requirement :-(