Multiple Thunderbolt buses to a single port?

[Kier-XF]

I suspect the answer to this is an obvious 'no', but I figured I'd ask anyway - are the three Thunderbolt buses on the 2021 MBPs tied specifically to a single Thunderbolt port each, or do they auto-configure themselves to be used where necessary?

For example, right now I have a Thunderbolt-connected display attached to each of the three ports on my MacBook Pro (which makes docking a bit of a pain), but it would be great if the system would/could detect if I had a single cable to something like a Thunderbolt 4 hub, with the displays hanging off that.

I'm going to assume that's not possible, but I'd be very happy for someone to inform me otherwise.

 

[killawat]

A lot of factors go into how much you can utilize from each port. The math gets fuzzy. Are your displays 6k? 5k? 4k? The ports don't allocate on the fly or move bandwidth between them or anything like that.

I suspect you'll be able to use a dock for 2 of your displays and will still need to plug one in directly to the Mac.

 

[Diablo360]

It all depends on what you’re running. I was able to run 2 x 49” monitors 5120 x 1440) through one USB C port.

 

[joevt]

You have an M1 Max MacBook Pro with three Thunderbolt ports and one HDMI port.

For M1 Macs, Thunderbolt buses are separate and each port belongs to its own Thunderbolt bus. A Thunderbolt bus has two DisplayPort connections to the GPU that can be used to connect one or two displays (original M1 Macs only support one display besides the built-in display or the HDMI display in the case of the M1 Mac mini).

The M1 Max MBP can connect 4 displays anyway you like with these limits: one or zero display for HDMI, zero, one, or two displays per Thunderbolt port. Two displays from a single Thunderbolt port requires a Thunderbolt display with a 2nd Thunderbolt port or a Thunderbolt dock or hub or adapter.

A tiled display like the LG UltraFine 5K display counts as one display for M1 Macs and two displays for an Intel Mac. In either case, it will use both DisplayPort connections of a Thunderbolt bus, so a second display cannot be connected to the same Thunderbolt bus.

The Apple Pro Display XDR (6K) and Apple Studio Display (5K) have tiled modes, but they also have a single tile mode using DSC which the M1 Macs will use, so you can connect two of these to a single Thunderbolt bus/port.

 

[Kier-XF]

A tiled display like the LG UltraFine 5K display counts as one display for M1 Macs and two displays for an Intel Mac. In either case, it will use both DisplayPort connections of a Thunderbolt bus, so a second display cannot be connected to the same Thunderbolt bus.

The Apple Pro Display XDR (6K) and Apple Studio Display (5K) have tiled modes, but they also have a single tile mode using DSC which the M1 Macs will use, so you can connect two of these to a single Thunderbolt bus/port.

That's precisely the info I was after, thank you @joevt. I guess that's one major bonus of the ASD over the LG5K that isn't really discussed, although in my case, a move to 3xASD vs 3xLG5K would actually only save me one cable, I'm not sure there's a compelling case yet.