Kensington Thunderbolt 5 Dock (SD5000T5)

[oldbee0x7]

Checked this on my M4 Max, looks like still only 2 ports.
If this is what's causing issue, is it possible to chain some more downstream devices to enabled more displays since the bandwidth is definitely enough. E.g. would there be some 'active' thunderbolt devices, or chain another dock? Would that sort of work as the Thunderbolt Display daisy chaining etc.

 

[oldbee0x7]

So just reading the support page here:

MacBook Pro with M4 or M4 Pro. You can connect up to two external displays in the following configurations:

• Connect one external display with up to 6K resolution at 60 Hz using a Thunderbolt port and one external display with up to 4K resolution at 144 Hz using the HDMI port.

MacBook Pro with M4 Max.You can connect up to four external displays in the following configurations:

• Connect up to three external displays with up to 6K resolution at 60 Hz using the Thunderbolt ports and one external display with up to 4K resolution at 144 Hz using the HDMI port.

Notice their wording between these two, "using a Thunderbolt port" and "using the Thunderbolt ports"....
is that sort of implying that one port can only support up to 2 displays? Well that really sucks then,

 

[joevt]

Checked this on my M4 Max, looks like still only 2 ports.
If this is what's causing issue, is it possible to chain some more downstream devices to enabled more displays since the bandwidth is definitely enough. E.g. would there be some 'active' thunderbolt devices, or chain another dock? Would that sort of work as the Thunderbolt Display daisy chaining etc.

If a Thunderbolt port on the Mac has only two DisplayPort In Adapters, then it cannot be used to connect more than two displays, no matter how many DisplayPort Out Adapters are added.

The GPU of the Mac is connected to the DisplayPort In Adapters of the Mac's host Thunderbolt controller. Thunderbolt DisplayPort tunnelling is used to get the DisplayPort data from the DisplayPort In Adapter to a DisplayPort Out Adapter of a downstream peripheral Thunderbolt controller of a Thunderbolt dock or display.

DisplayPort tunnelling can be used to get a DisplayPort signal from one Mac to a Thunderbolt 1 iMac - this is called Thunderbolt Target Display Mode. The Thunderbolt 1 iMac has a Thunderbolt 1 controller with a DisplayPort Out Adapter for this purpose.

Notice their wording between these two, "using a Thunderbolt port" and "using the Thunderbolt ports"....
is that sort of implying that one port can only support up to 2 displays? Well that really sucks then,

This wording does not say that more than one port is necessary to connect 3 displays.
This wording does not say that one port can be used to connect 3 displays.
They are careful about what they say. They don't give a fsck about what they do not say.

 

[oldbee0x7]

Checked with apple online support chat, they said that you can only connect 2 monitors for one port, for a third one you need to connect it to another port, and "There is a hardware limitation which we cannot pass"

 

[DaveOP]

I was looking for the entire file compressed into a zip file and attached to a reply post. The relationship of the Thunderbolt devices is important. Here's a screenshot from IORegistryExplorer.app for an M1 Mac mini from 2021. It shows two DP In Adapters per Thunderbolt port.
View attachment 2459701


DSC should not be required if the displays use less bandwidth than Thunderbolt 5 supports.

Three 4K60 displays should work. They use HBR2 x4 which is 17.28 Gbps. x3 = 51.84 Gbps. 5K60 and 6K60 displays that use DSC will use HBR2 x4.

Three 4K120 displays might not work if they don't use DSC. They use HBR3 x4 which is 25.92 Gbps. x3 = 77.76 Gbps. Hmm. Seems like it should work since it's less than 80 Gbps. Or it should switch the Thunderbolt 5 output to asymmetric mode (120 Gbps transmit, 40 Gbps receive).

If a display doesn't use DSC, then you might be able to force a display to use DSC by connecting it to a DisplayPort MST Hub that supports DSC. The MST Hub might use HBR3 x4 though, unless you force it to use HBR3 x2 - by disabling two of the SuperSpeed pins, or by using a USB-C dock that supports MST and USB 3.x. The CalDigit SOHO is such a dock but it's DSC mode does not support 10bpc decompression for displays that don't support DSC.

Here you go. Sorry for the delay.

 

[joevt]

Here you go. Sorry for the delay.

For acio0, there's a Thunderbolt 5 host controller (the Mac) with two DP In Adapters.
Connected to that is a Thunderbolt 5 peripheral controller (the dock) with three DP Out Adapters (one more than Thunderbolt 3/4 would have).
The DP In Adapters are connected to two DP Out Adapters. The third DP Out Adapter has no connection and it never can because there's only two DP In Adapters.

A Thunderbolt 5 host has one each PCI and USB Down Adapters per port, same as Thunderbolt 4.
Apple Silicon has one port per host controller, same as Thunderbolt 4.

A Thunderbolt 5 peripheral has one each PCI and USB Up Adapters, and three each PCI and USB Down Adapters, same as Thunderbolt 4.

The USB4 v2 spec can probably be used to interpret these: "Remote DP Capabilities", "Cached Local DP Capabilities", "Cached Common DP Capabilities".
Just search for "Maximal DPCD Rev".

acio1 has a Thunderbolt 4 device with a display. It only has two PCI Down Adapters (because one of the ports is hard coded as DisplayPort Out only?).

acio2 has no Thunderbolt device connected (but it could have USB connected which are listed in some other acio2 related node of the ioreg).

 

[joevt]

Here you go. Sorry for the delay.

To be clear, this is for a M4 Max MBP? The first post said M4 Pro/Max MBP.

 

[DaveOP]

To be clear, this is for a M4 Max MBP? The first post said M4 Pro/Max MBP.

M4 Max, fully spec'd out on cores.

 

[joevt]

M4 Max, fully spec'd out on cores.

Guess we'll have to wait for M5 to get 3 displays from an Apple Thunderbolt 5 port. Even then they may decide that two displays per port is enough.