@lightemperor Happy to help! The Mini-DisplayPort ports are the pair of ports next to the MagSafe charger connector. They’re also called Thunderbolt 2 ports since they support that, but the physical connector type is Mini-DisplayPort and they can work as regular Mini-DisplayPort video outputs.
@lightemperor If you want to use the KVM function, you need both video and USB data connections between each source system and the display. HDMI only carries video, so for that system you'll need to run a separate USB cable from the USB-B "upstream USB port" on the display to either a USB-A or USB-C port on your MacBook. For the new MacBook, a USB-C to USB-C connection can carry video and USB data over a single cable, as well as power to charge your MacBook.
Note however that depending on how old your "old MacBook" is, it might not be able to run your U3219Q at its native setup of 4K 60 Hz. As a general bit of advice, when asking for technical answers or assistance, it helps to provide basic technical information so that the people here who are willing to help have something to work with. In this case, identifying the exact MacBook models involved would have been helpful. Apple has made several generations, sizes, and product lines of MacBooks (Air, Pro, "regular" MacBooks), all of which have different ports and capabilities, and if that information had been clear I could have recommended the exact cables you'd want and let you know what you could expect from your old MacBook in terms of display support capabilities.
@lightemperor Two quick additional notes: First, the USB 3.0 cable that came with the display is exactly what you'll need to use to get a USB data path to your mid-2015 MacBook, since that system still has USB-A "regular USB" ports. And second, be aware that USB speeds over the USB-C interface are limited to USB 2.0, not USB 3.x. If you're only planning to connect a keyboard and mouse to the display's USB ports, that's not a problem, but you may want to avoid connecting something like an external hard drive that way, since those types of devices will be bottlenecked for the system connected via USB-C. I wrote a post in this thread explaining why this limitation exists. Normally if you wanted to use USB-C and get USB 3.x, you could use that upstream USB 3.0 port, but since you're planning to use the display with two different systems, that upstream port won't be available to the USB-C system.
@lightemperor If you've got a mid-2015 MacBook Pro 15-inch, then according to Apple's tech specs, the HDMI output will only run 4K at 30 Hz -- but I'm pretty sure the Mini-DisplayPort output will run 4K 60 Hz. So rather than using an HDMI cable, grab a Mini-DisplayPort to DisplayPort cable. In terms of switching, the display's on-screen menu should allow you to assign each video input to the correct upstream USB data path (the USB-C port could technically be used as a data-only connection), and after that then yes when you switch video inputs, the display will switch the active upstream USB data path accordingly. The User Guide for that display here might help clarify how it all works. Good luck!
jphughan
9 Legend
•
14K Posts
0
May 25th, 2021 22:00
@lightemperor Happy to help! The Mini-DisplayPort ports are the pair of ports next to the MagSafe charger connector. They’re also called Thunderbolt 2 ports since they support that, but the physical connector type is Mini-DisplayPort and they can work as regular Mini-DisplayPort video outputs.
jphughan
9 Legend
•
14K Posts
0
May 25th, 2021 21:00
@lightemperor If you want to use the KVM function, you need both video and USB data connections between each source system and the display. HDMI only carries video, so for that system you'll need to run a separate USB cable from the USB-B "upstream USB port" on the display to either a USB-A or USB-C port on your MacBook. For the new MacBook, a USB-C to USB-C connection can carry video and USB data over a single cable, as well as power to charge your MacBook.
Note however that depending on how old your "old MacBook" is, it might not be able to run your U3219Q at its native setup of 4K 60 Hz. As a general bit of advice, when asking for technical answers or assistance, it helps to provide basic technical information so that the people here who are willing to help have something to work with. In this case, identifying the exact MacBook models involved would have been helpful. Apple has made several generations, sizes, and product lines of MacBooks (Air, Pro, "regular" MacBooks), all of which have different ports and capabilities, and if that information had been clear I could have recommended the exact cables you'd want and let you know what you could expect from your old MacBook in terms of display support capabilities.
lightemperor
4 Posts
0
May 25th, 2021 22:00
@jphughan Thanks for the in-depth reply! My MacBook is MacBook Pro mid 2015. Will that support it?
Also, after I connect all the cables, will changing input auto switch the inputs to the right monitor?
lightemperor
4 Posts
0
May 25th, 2021 22:00
@jphughan .Thanks for everything! I’ll reply again if any issues come up with this solution
lightemperor
4 Posts
0
May 25th, 2021 22:00
@jphughan thanks for all the help. This all makes a lot of sense.
just as a final clarification, I don’t think my MacBook has a mini display port? Or at least I don’t think it does (have never used a DP port before)
Thanks again!
jphughan
9 Legend
•
14K Posts
0
May 25th, 2021 22:00
@lightemperor Two quick additional notes: First, the USB 3.0 cable that came with the display is exactly what you'll need to use to get a USB data path to your mid-2015 MacBook, since that system still has USB-A "regular USB" ports. And second, be aware that USB speeds over the USB-C interface are limited to USB 2.0, not USB 3.x. If you're only planning to connect a keyboard and mouse to the display's USB ports, that's not a problem, but you may want to avoid connecting something like an external hard drive that way, since those types of devices will be bottlenecked for the system connected via USB-C. I wrote a post in this thread explaining why this limitation exists. Normally if you wanted to use USB-C and get USB 3.x, you could use that upstream USB 3.0 port, but since you're planning to use the display with two different systems, that upstream port won't be available to the USB-C system.
jphughan
9 Legend
•
14K Posts
1
May 25th, 2021 22:00
@lightemperor If you've got a mid-2015 MacBook Pro 15-inch, then according to Apple's tech specs, the HDMI output will only run 4K at 30 Hz -- but I'm pretty sure the Mini-DisplayPort output will run 4K 60 Hz. So rather than using an HDMI cable, grab a Mini-DisplayPort to DisplayPort cable. In terms of switching, the display's on-screen menu should allow you to assign each video input to the correct upstream USB data path (the USB-C port could technically be used as a data-only connection), and after that then yes when you switch video inputs, the display will switch the active upstream USB data path accordingly. The User Guide for that display here might help clarify how it all works. Good luck!