Using two displays with a Latitude 5400 without a dock

@Freaker95  Happy to help, but you seem to have gotten the wrong takeaway from my reply.  Daisy chaining is an option, as long as you're ok having only USB 2.0 data speeds available.  You just have to set the option I mentioned above.  But if you want USB 3.x data speeds available with your P2421DC, then use connecting that display via USB-C and your other display via HDMI would be an option too.

@jphughan thanks for the quick response!

So daisy chaining will not be an option for a Latitude 5400 with no TB3 connection?

And can I connect 2x P2421D monitors by connect 1 to the HDMI and 1 to the USB-c port, both getting the 2540x1440 resolution?

@jphughan 

Ah sorry, my bad, I see it now! 

So I have 2 options:

1. Daisy chaining the P2421DC and P2421D to get the 2540x1440 resolution by setting the DC monitor to High Resolution mode. But then my USB ports have max 2.0 speed (instead of USB 3.0) which is not a problem for me!

2. One monitor connecting to the USB-C and one monitor to the HDMI --> resulting in both 2540x1440 resolution and the USB 3.0 speed

Right?

@Freaker95 The Latitude 5400 only supports DisplayPort 1.2/HBR2 over USB-C.  Therefore in order to run enough video bandwidth for dual 2560x1440 60 Hz, the USB-C link will have to be limited to USB 2.0 data speeds, which means if you connected USB 3.x devices to the USB ports built into the P2421DC, they would only run at USB 2.0 speeds.  But the P2421DC offers a USB-C Prioritization option to allow you to set up this mode.  You'd have to set it to High Resolution, which maximizes video bandwidth while limiting USB data to 2.0.  The High Data Speed mode allows USB 3.x but then cuts video bandwidth in half.  On a DisplayPort HBR2 system, a half-bandwidth link is only enough to run a single 2560x1440 60 Hz display -- so that mode would be useful only if you were NOT daisy chaining.  (A newer DisplayPort HBR3 system would be able to run dual 2560x1440 60 Hz and USB 3.x simultaneously.)

Hi @jphughan ! 

I have a Latitude 5400 as well (usb-c with no TB3). So I can connect this laptop then to a P2421DC and P2421D by daisy chaining and the usb-c, both getting the 2540x1440 60Hz resolution?

So:
Latitude 5400 <-- usb-c --> P2421DC <-- displayport cable --> P2421D

Hopefully you can advice me! 

@Freaker95  Correct.   The only asterisk to the daisy chain setup is that I remember someone else once trying to set up a daisy chain like this and somehow they could never get dual 2560x1440 even after setting USB-C Prioritization to High Resolution.  I don't think that was ever resolved since they resorted to just connecting each display directly.  Unfortunately not everything that should work in the tech world always actually does.  I don't have direct personal experience with your specific system or those display models, but it should work.  But if it doesn't, the fallback of connecting one via HDMI would be fine.  Good luck!

@jphughan Thanks for the quick responses man! Appreciate it! 

@jphughan just one more question...

Besides a dual monitor setup... I'm considering to connect my Latitude 5400 (usb-c, but with no TB3) to a single Dell U3419W, with a 3440x1440 resolution and a 21:9 ratio, 60Hz.

Is it possible to connect my Latitude 5400 to this U3419W by the USB-C connections? Not only for the resolution of 3440x1440 but also the 21:9 ratio?

Thanks again in advance! 

@jphughan also in terms of the 21:9 ratio? Or has that nothing to do with it, and is the resolution only the determined factor? Not that I will get black bars or a stretched screen?

@Freaker95 Yes, that system will run 3440x1440 over USB-C.

@Freaker95  3440x1440 is a 21:9 aspect ratio resolution, so if a system can run 3440x1440, then by definition it can run a 21:9 aspect ratio.

@Freaker95  That's a limit on the HDMI 1.4 port.  The GPU can support 4K 60 Hz.  You can verify this by going to ark.intel.com and looking up the specs for your system's CPU.  The maximum resolution limitations inherent to the GPU and any limitations inherent to the particular output you're using are completely independent of each other, and your intended display setup has to fit within the limitations of both.  Fortunately, the USB-C port exposes a DisplayPort 1.2 interface, which can carry enough bandwidth to run 4K 60 Hz, and therefore more than enough to run 3440x1440.

@jphughan I also saw this now in the User Guide of the Latitude 5400. (Max 4096x2304 at 24Hz). Or has that nothing to do with the usb-c connection?

https://dl.dell.com/topicspdf/latitude-14-5400-laptop_owners-manual2_en-us.pdf (Page 16)

@Freaker95  Happy to help.  I'm an IT professional, so I contribute here as sort of my "pro bono" work to try to do some good in the world.  Nobody's paying me to do it.