Will the iMac 5k + 4k Monitor thru Mini Display Port work at 60Hz Full Resolution?

[nemoryoliver]

Hi guys! I wanted a 2nd monitor for my iMac 27" 2019, but don't want to spend much on a thunderbolt/usb-c monitor. I am looking at this Samsung Monitor LU28E590D5 https://s.lazada.com.ph/s.upKN it's the cheapest 4k monitor with IPS panel. I'm hoping I can make it work at full 4k resolution @ 60Hz before I purchase it. Can anyone with experience confirm?

Thank you very much.

 

[mikehalloran]

Relax.

Ok, there’s no such thing as a Thunderbolt 3 monitor. USB-C is just a port that carries many protocols—on your iMac, it carries TB3 and video (and audio etc.). So-called TB3 monitors pass 45–65W power to charge other devices and at least one passes full TB3. If you don’t need that functionality, you don’t need a TB3 monitor.

You need a USB-C to DisplayPort or HDMI cable. $10–$16 or so. Some report that adapters are problematic so I recommend cables. There are a few monitors that only have full resolution and functionality with DisplayPort but most are just as good either DP or HDMI.

There are very few 5K monitors on the market. The 4 from LG require a TB3 connection to hook up to a Mac. The other one can only output 5K via DisplayPort 1.4 and only the late 2018 MacBook Pro supports this (till the new Mac Pro ships, at least).

 

[Ledgem]

Hi guys! I wanted a 2nd monitor for my iMac 27" 2019, but don't want to spend much on a thunderbolt/usb-c monitor. I am looking at this Samsung Monitor LU28E590D5 https://s.lazada.com.ph/s.upKN it's the cheapest 4k monitor with IPS panel. I'm hoping I can make it work at full 4k resolution @ 60Hz before I purchase it. Can anyone with experience confirm?

Thank you very much.

To answer your question about the model you're looking at... it supports input through HDMI and Displayport. Based on what I can find, it has both HDMI 1.4 (slot 1) and HDMI 2.0 (slot 2) inputs. Your Mac does support 4K at 60 Hz when using HDMI 2.0, so as long as you use a HDMI 2.0-supporting cable and connect to that second slot, you should be able to use the display at full 4K resolution and at the 60 Hz refresh rate. You will need a HDMI to USB-C adapter that also supports HDMI 2.0. You could probably use the Displayport connector, too, but you'll need an adapter for that as well, as the Displayport type used by this monitor is the crooked D-shaped connector that Macs do not carry. The monitor supports Displayport 1.2, which would be able to run 4K resolution at 60 Hz as well.

 

[nemoryoliver]

To answer your question about the model you're looking at... it supports input through HDMI and Displayport. Based on what I can find, it has both HDMI 1.4 (slot 1) and HDMI 2.0 (slot 2) inputs. Your Mac does support 4K at 60 Hz when using HDMI 2.0, so as long as you use a HDMI 2.0-supporting cable and connect to that second slot, you should be able to use the display at full 4K resolution and at the 60 Hz refresh rate. You will need a HDMI to USB-C adapter that also supports HDMI 2.0. You could probably use the Displayport connector, too, but you'll need an adapter for that as well, as the Displayport type used by this monitor is the crooked D-shaped connector that Macs do not carry. The monitor supports Displayport 1.2, which would be able to run 4K resolution at 60 Hz as well.

Hi Ledgem,

Thank you very much for your answer. I am happy to know that with this monitor it's possible to get it running at full resolution and at 60Hz through HDMI 2.0. By searching USB C to HDMI cables, I already saw some that mentions it can support 4k so I guess these are the cables I need. https://www.lazada.com.ph/products/...o4l.searchlist.list.5.289538acjJWgOY&search=1

 

[theluggage]

By searching USB C to HDMI cables, I already saw some that mentions it can support 4k so I guess these are the cables I need.

...or a USB C to DisplayPort cable: I use one of these on a 2017 iMac to drive a 4k@60Hz display:
https://plugable.com/products/usbc-dp/

I do recall an issue with some older DP and HDMI adapter cables not working on 2017 or later Macs, so if you can find one that (like the Plugable one above) explicitly says it works with 2017 iMacs (or that you can confirm that someone else has used) that would be reassuring. Of course, you have to go with whatever you can get in the Philippines...

Ok, there’s no such thing as a Thunderbolt 3 monitor.

Yes, there are Thunderbolt 3 monitors and they work quite differently from "USB-C" monitors.

Thunderbolt 3 monitors use the Thunderbolt 3 protocol. They require both the computer and the monitor to have Thunderbolt controllers because although Thunderbolt does use DisplayPort internally, what goes down the cable is a thunderbolt signal which combines two DisplayPort streams plus PCIe data (which can drive USB controllers, Ethernet ports etc. in the monitor) into a single signal. Because a Thunderbolt signal can contain two DisplayPort 1.2 streams you can have 5k displays without needing DisplayPort 1.4, or you can run two 4k@60Hz displays from a single TB port while, at the same time, supporting full-bandwidth USB 3.1 ports or other devices in the display.

"USB-C" monitors use USB-C's "DisplayPort Alt Mode" which physically uses some of all of the USB-C cable's wires to carry a single stream of DisplayPort signals. You can't connect multiple displays to a single port because the Mac doesn't support multi-displays per DP stream (although that is part of the DP spec). If you connect a 4k@60Hz display with DisplayPort 1.2 then all 4 of the cable's high-speed data pairs are needed for display data and all that's left for USB "docking" is a low-speed USB2 pair. Even with a standard-def display, USB C only supports a single USB 3.1 'stream' that can drive a USB hub in the display - TB3 can support multiple, full-bandwidth USB 3.1 controllers in a display or dock.

Also, although I think that, initially, only TB3 offered 100W charging, that's now part of the USB Power Delivery Standard and isn't a distinction between TB3 and "USB-C" - in any case, the full 100W was never compulsory for either so you still have to check that the hub/display/cable all support full power.

The Apple/LG Ultrafine 5k display is Thunderbolt 3 only, not "USB-C". The old Apple/LG true-4k display used to be "USB-C" (i.e. USB-C DP1.2 Alt Mode) - the new model that replaced it a few months back is Thunderbolt 3 and "USB-C". There are several other "USB-C" displays on the market, and a few "true" TB3 ones (mostly ultra-wide).

USB-C is just a port that carries many protocols

Well... technically "USB-C" refers to the type of multi-protocol connector... unfortunately, back in the real world, "USB-C" is widely (ab)used to mean "USB 3.1 over type-C" or "USB-C in DisplayPort Alt mode" or "USB power delivery version x" or whatever the user intended it to mean. Its not very helpful to tell people that "USB-C is just a connector" even if that is pedantically correct, because that's simply not how the term gets used.

Yes, its a mess (see also USB 3.1 products being sold as "TB3 compatible" simply because they have USB-C connectors...)

 

[mikehalloran]

Some of the gaming protocols are not supported on a Mac via HDMI but are with DP 1.2. That’s why I recommend a USB-C to DisplayPort cable, not adapter.

If you aren’t a gamer, none of this is an issue.