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P2422HE, S2721D, USB Type-C, daisy chain help
Hello everyone.
I am thinking about buying dual monitor setup for work and personal use, but I'd really appreciate if I could get some confirmation if my plan is logical and will it work in general. I was thinking about P2422HE as main monitor and s2721D as the second monitor.
My setup in theory would look something like this: Lenovo T480s connected via type-c to P2422HE, then S2721D connected via Displayport to P2422HE.
Because P2422HE monitor is a fullHD monitor and S2721D is a QHD monitor, will S2721D monitor maintain its native resolution as a second monitor? Also, will things change if the lid of my laptop will be open or closed?
Also, from what I read, P2422HE can power a laptop up to 65W, so will this power output will be enough or will I have to connect external power brick to charge laptop with 2 monitors connected?
Or should I not mix monitor sizes and resolutions and stick to two QHD 27inch or fullHD 24inch monitors.
Thank you in advance for the help.
jphughan
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July 16th, 2021 10:00
@Trance-fighter The T480s only supports DisplayPort 1.2/HBR2 over USB-C, and the U2422HE sets up the USB-C link to carry both video and USB 3.x data. Carrying USB 3.x data cuts video bandwidth in half, and half of a DP 1.2/HBR2 interface isn't enough for FHD+QHD. Dell's U Series QHD and 4K displays allow you to configure the display to instead set up the USB-C link for full video bandwidth with the tradeoff of only having USB 2.0 speeds available, but that isn't offered on the FHD displays, and I'm not sure it's offered on any P Series displays at all. I guess Dell doesn't really plan for use cases where the downstream display in a daisy chain has a higher resolution than the first one. But if you for example bought the U2722DE, you'd be able to configure the USB-C Prioritization setting to High Resolution, in which case you could run a dual QHD daisy chain over USB-C, as long as you were ok accepting USB 2.0 data speeds, which might be fine based on what you planned to plug into the display's USB ports.
Otherwise, a USB-C to DisplayPort cable would give you full video bandwidth and therefore allow you to run FHD+QHD in a daisy chain, but then you don't have any USB data at all or power running over that cable.
Another option would be to connect the QHD display directly to the system's built-in HDMI output. That of course results in two cables, but it allows you to run both displays at their native resolution and continue having video, power, and USB 3.x data running to the P2422HE.
But if you want an FHD+QHD display setup, USB 3.x data, and power all running over a single cable with that system, you'd need a Thunderbolt dock, like Lenovo's ThinkPad Thunderbolt 3 Dock Gen 2.
Trance-fighter
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July 16th, 2021 14:00
Thank you @jphughan for such a quick reply. Since I am on a budget, and I'm trying to decide which setup would be easier to implement and your insight was very helpful. Before that I did not know that I have to be aware of different interfaces and bandwidths when deciding on monitors and connections between them.
So in my case, if I want co connect QHD and FHD monitors, best setup would be to connect laptop via type-c to p2422HE or P2419HC and then connect QHD monitor via HDMI to laptop.
In other case, I should use two FullHD monitors and then link them using Daisychain: type-c from laptop to monitor and then displayport between monitors.
Do I understand correctly my options?
jphughan
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July 16th, 2021 15:00
@Trance-fighter Happy to help. Yes, those options would work. Another one I’ll mention since it sounds like you haven’t bought the display yet would be to get a QHD USB-C display like the U2722DE, which has the option to configure the USB-C link to maximize video bandwidth by keeping USB to USB 2.0 speeds. In that case you could run a dual QHD daisy chain if you wanted. But of course that display is more expensive and you’d be limited to USB 2.0. Good luck!
Trance-fighter
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July 17th, 2021 08:00
Again, thank you for the help. You are correct, I haven't bought the monitors yet, so I was looking for the best cost/quality solution and didn't want to overpay for something that I won't be able to fully utilize. Since now I know what are my best options are, purchasing decision became that much easier.