How many LG Ultrafine 5K's or Dell UP2715K's will this drive?

[rkuo]

Well, once again the display capabilities of a new Mac are a little vague in a new model launch. The dual link Displayport shenanigans in these external 5K monitors has always been a sore point.

From what I can gather, the M1 Max in the Macbook Pro's can drive triple LG UltraFine 5K's at full res (based on an apple support article for that monitor). The spec page for the Mac Studio says it can drive 4 Pro Display XDR's and 1 HDMI output ... which is not quite the same thing, as LG UltraFine 5K's are actually 6 display lanes due to the uncompressed dual link connections.

Even more odd is that the M1 Ultra provides two extra thunderbolt ports on the front. Shouldn't the M1 Ultra be able to support even MORE displays since it has a whole extra M1 Max tacked on, which is presumably how the extra TB4 ports are getting serviced? Might be an oversimplification, but it's a valid question.

 

[Hessel89]

6

 

[joevt]

I think 4. These dual tile 5K displays take two DisplayPort connections per Thunderbolt port. Each Thunderbolt port is a separate Thunderbolt bus which can source two DisplayPort connections, so each Thunderbolt port can support one dual tile display or two single tile display. This does not mean you can connect 8 single tile displays - as the 4 extra DisplayPort connections are only available for tiled displays.

4 dual tile displays + one HDMI display means 9 DisplayPort connections. Maybe there's a limit of 8? In that case you couldn't connect a display to HDMI if you have 4 dual tile displays connected.

There was one person that successfully got 3 LG UltraFine 5K displays, an HDMI display, and the built-in display working at the same time for an M1 Max MacBook Pro. That's 8 DisplayPort connections.

Given that, one might expect the M1 Ultra should be able to do 6 displays but Apple says both M1 Max and M1 Ultra support the same number of displays which is 4 (plus one from HDMI). It's like you might expect the M1 Mac mini to support at least two displays from Thunderbolt, but it only allows one.

 

[rkuo]

I think 4. These dual tile 5K displays take two DisplayPort connections per Thunderbolt port. Each Thunderbolt port is a separate Thunderbolt bus which can source two DisplayPort connections, so each Thunderbolt port can support one dual tile display or two single tile display. This does not mean you can connect 8 single tile displays - as the 4 extra DisplayPort connections are only available for tiled displays.

4 dual tile displays + one HDMI display means 9 DisplayPort connections. Maybe there's a limit of 8? In that case you couldn't connect a display to HDMI if you have 4 dual tile displays connected.

There was one person that successfully got 3 LG UltraFine 5K displays, an HDMI display, and the built-in display working at the same time for an M1 Max MacBook Pro. That's 8 DisplayPort connections.

Given that, one might expect the M1 Ultra should be able to do 6 displays but Apple says both M1 Max and M1 Ultra support the same number of displays which is 4 (plus one from HDMI). It's like you might expect the M1 Mac mini to support at least two displays from Thunderbolt, but it only allows one.

Very interesting ... I hadn't been following this topic recently but as someone running 3 UP2715K's this is still a nightmare of weird implementation details and dependencies! Would never have imagined this would be the case 5 years later and with no real mainstream alternatives to boot.

I have the M1 Max Studio on order and a couple of TB3 to dual displayport adapters coming. Will see how that goes and then hopefully work up to the third display or swap it out for the new studio display.

 

[joevt]

Very interesting ... I hadn't been following this topic recently but as someone running 3 UP2715K's this is still a nightmare of weird implementation details and dependencies! Would never have imagined this would be the case 5 years later and with no real mainstream alternatives to boot.

I have the M1 Max Studio on order and a couple of TB3 to dual displayport adapters coming. Will see how that goes and then hopefully work up to the third display or swap it out for the new studio display.

I would definitely get a third TB3 to Dual DisplayPort adapter for the third UP2715K. I think the UP2715K is the same size as the Studio display and is bright enough so I don't know why you would want to get a studio display unless you have other computers to connect the UP2715K to or you need a camera. Maybe the uniformity of the three UP2715K is preferable to having two UP2715K and one Studio which might be brighter than its neighbours.

The adapters will use up 3 of your TB4 ports, leaving only one remaining. In that case you might want a TB4 dock or hub to add more TB4 ports.

Each UP2715K will use up ≈29 Gbps of Thunderbolt bandwidth (but mostly just transmit bandwidth). So Thunderbolt devices that can do more than 11 Gbps write speed should be connected to the unused TB4 port (maximum write speed is ≈23 Gbps).

 

[rkuo]

I would definitely get a third TB3 to Dual DisplayPort adapter for the third UP2715K. I think the UP2715K is the same size as the Studio display and is bright enough so I don't know why you would want to get a studio display unless you have other computers to connect the UP2715K to or you need a camera. Maybe the uniformity of the three UP2715K is preferable to having two UP2715K and one Studio which might be brighter than its neighbours.

The adapters will use up 3 of your TB4 ports, leaving only one remaining. In that case you might want a TB4 dock or hub to add more TB4 ports.

Each UP2715K will use up ≈29 Gbps of Thunderbolt bandwidth (but mostly just transmit bandwidth). So Thunderbolt devices that can do more than 11 Gbps write speed should be connected to the unused TB4 port (maximum write speed is ≈23 Gbps).

It's more about my current setup and work requirements ... the center dell is bubbling under the glass as the top (so I will probably replace it with a new single cable display). Additionally, I also need to run the intel mac I have now (I will be working on porting some mac/x86 code to arm) and that has to take at least one of the monitors. Eventually when the porting work is successful I'm hoping to run all three monitors off the Mac Studio.

 

[e-dub]

A question: If I want to run a pair of LG 5k displays, will a 32 core Max make a difference vs a 24?

 

[BanditoB]

@e-dub

The number of GPU cores has no impact on how many monitors can be attached to the system. The extra GPU cores will provide a performance boost for graphics-intensive applications however.

 

[e-dub]

@e-dub

The number of GPU cores has no impact on how many monitors can be attached to the system. The extra GPU cores will provide a performance boost for graphics-intensive applications however.

10-4. Thank you!

 

[rkuo]

I can now verify 3 Dell UP2715K's work with the StarTech TB3 to Dual Displayport adapters on my Mac Studio Ultra. Sometimes one of the monitors glitches on wakeup displaying half the screen or not waking up at all and requires a power down/up to get back in sync, but this has always been sort of an issue with these monitors so I don't know how much of this is on the Mac Mini.

I may be able to test with more MST monitors eventually, we'll see.

 

[joevt]

I can now verify 3 Dell UP2715K's work with the StarTech TB3 to Dual Displayport adapters on my Mac Studio Ultra. Sometimes one of the monitors glitches on wakeup displaying half the screen or not waking up at all and requires a power down/up to get back in sync, but this has always been sort of an issue with these monitors so I don't know how much of this is on the Mac Mini.

I may be able to test with more MST monitors eventually, we'll see.

The Dell UP2715K is a dual link SST display, not MST (same as all 5K or larger tiled displays)
4K dual tile MST displays (old displays that existed before 4K could be done with SST) don't actually work on M1 Macs (at least that's what I've seen from one person with an M1 Mac) but do work on Intel Macs.