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P2715Q, two, daisy chain, Macbook Pro 13"
Hey all! I only have the two ports for my Macbook Pro 13". I am trying to find a way to daisy chain the two P2715Q monitors so they only need to connect into one port on my MacBook Pro. This way I can have another port to connect my charger. I have one DP cable that can connect from the monitor directly to the MacBook Pro. The other DP cable I've plugged from one monitor to another, but all I get is a duplication of the monitor connected to the laptop. Any recommendations? Any insight would be great!
Thanks in advance
jphughan
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July 1st, 2020 17:00
@AXRG Unfortunately macOS still does not support DisplayPort MST, which is necessary for daisy chaining. There have been complaints about this for several years on the Apple forums, these forums, and elsewhere on the Internet. A cloned image is what happens when you connect a daisy chain setup to a system that doesn't support MST. Ironically if you install Boot Camp on your Mac in order to run Windows, then you can get daisy chaining working, so the hardware supports it. It's macOS that doesn't.
As a result, the only way to run multiple displays from a single connection on a Mac is to use a solution that taps into Thunderbolt 3. The reason that works is that TB3 allows the system to send two independent GPU outputs over the TB3 link, so the Mac assigns one output to each display. But even there you can only run TWO displays over TB3, whereas on a PC you'd be able to run 3-4 depending on the PC and the displays involved. But DisplayPort MST requires the system to be able to split a SINGLE interface to drive multiple displays, and it seems Macs still don't allow that. Since the P2715Q isn't a native Thunderbolt 3 display, the only way you could connect two displays to a single port on your Mac (while running macOS) would be with a Thunderbolt 3 to Dual DisplayPort adapters. StarTech, Sabrent, Sonnet, Plugable, and Nekteck all make a product like that. I haven't personally used any of them, but I've used other products made by all of them because they're all solid vendors. Make sure you get one that specifically mentions Mac compatibility, because some early variants of those products used a Thunderbolt 3 chipset that Apple decided not to support, so those products only ended up working on Windows PCs.
jphughan
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July 1st, 2020 17:00
@AXRG In addition to my above reply, if it helps take the sting out of having to buy extra equipment to get your setup working as you want, you wouldn't have been able to daisy chain dual 4K 60Hz displays from a 13" MacBook Pro anyway, unless you were ok with both of them running at only 30 Hz. The 13" MacBook Pro only supports DisplayPort 1.2/HBR2, and a single DisplayPort 1.2 interface, which is all you get with daisy chaining, does not provide enough bandwidth to run dual 4K 60Hz. Thunderbolt 3 taps into two DisplayPort interfaces, which is why it will work. And the last few generations of 15" MacBook Pros have supported DisplayPort 1.4/HBR3, which DOES have enough bandwidth in a single interface for dual 4K 60Hz displays -- but actually the P2715Q itself only supports DisplayPort 1.2, so that wouldn't have worked either.
You may want to turn off the MST feature on your displays, because if you keep it enabled, I believe the displays will limit themselves to only running at 30Hz specifically to ensure enough bandwidth is available to pass through to a daisy chained display. The idea here is that if you enable daisy chaining, then presumably you want to run a second display, so the display reduces its bandwidth requirements by reducing its refresh rate. But that of course means that you're not running that display at its maximum capability.
So to sum up: Disable MST on both of your P2715Q so that they'll allow 4K 60Hz. Then get a TB3 to Dual DP adapter that specifically mentions Mac support, and you should be good to go.
jphughan
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July 1st, 2020 17:00
@AXRG Sorry for the triple post here, but I just realized you didn't technically specify that you had a 13" MacBook Pro that supports Thunderbolt 3. Everything I wrote above assumes that you have one of those. If you have an old 13" MacBook Pro that only supports Thunderbolt 2, I'm not sure what your options would be since I haven't looked into that scenario. But either way, as a general tip for the future, when asking for help with technical issues like this, it helps to provide technical information, in this case the generation of 13" MacBook Pro you're running.
Yang2018
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August 29th, 2020 00:00
Sorry for bringing up this old thread, but I am wondering if in principle a single display port 1.2 could support one 4K display at 60 Hz plus a 1080 P display at 60 Hz?
Yang2018
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August 29th, 2020 00:00
I have an older 15inch MacBook pro mid-2015 with AMD Radeon R9 M370X.
I have P2415Q and U2311H. I wonder if a TB2- dual DP adaptor might work? I almost bought a Dp-DP cable to try daisy chain from 2415q to 2311h..
jphughan
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August 29th, 2020 08:00
@Yang2018 I haven't seen a TB2 to Dual DP adapter, and I don't think a single Thunderbolt 2 port has enough bandwidth to run 4K 60 Hz + 1080p, although I may be wrong on that. (I'm also not sure that TB2 supported having dual source GPU interfaces wired to it the way TB3 does, and if it only has one interface, then the fact that macOS doesn't support DP MST means that TB2 to Dual DP wouldn't work anyway, regardless of bandwidth concerns.) Given that the 15" MBP mid-2015 model has 2x TB2 ports plus HDMI, I would suggest connecting the displays separately. If you use the HDMI output, connect the U2311H there, since that system's HDMI output won't handle 4K 60 Hz. The TB2 ports can, though, and if you want to connect one or both displays to those ports, just use MiniDP to DP cables.