Hi everyone. I just recently bought a CalDigit TS3+ for my M1 mac and it's working well. Although it's got a lot of ports, I'm already itching for more. I've got a new 14" M1 MBP on the way in early December and I was curious if anybody knows if it's possible two connect TWO TS3+ docks to the same computer? Has anyone done something like this? Thanks!
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How many CalDigit TS3+?
- Thread starter ndriver182
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Charging isn't my main concern. I'm just looking for access to even more ports. I wanted to make sure that having two plugged in wouldn't damage something somehow or if i wouldn't be able to take full advantage of the ports on the 2nd hub.
Caldigits Elements hub has more Thunderbolt ports and more 10GB/s USB ports than the TS3+ but less of other kinds, so, as above, it depends what you need.
You can connect as many as you like - you can even daisy chain them off of each other if you really had to.....
daisy chain - 5 thunderbolt devices per Thunderbolt/USB4 port of your M1 Mac.
6 devices per Thunderbolt port of an Intel Mac.
Actually, that's only for the length of the chain. Now that there exists Thunderbolt 4 hubs or docks with 3 downstream Thunderbolt ports, the width can be expanded by x3 for each level.
With no hubs, you can connect 5 Thunderbolt devices ((3^0)x(5-0))
With 1 hub, you can connect 12 Thunderbolt devices ((3^1)x(5-1))
With 2 levels of hubs (1+3 hubs) you can connect 27 Thunderbolt devices ((3^2)x(5-2))
With 3 levels of hubs (1+3+9 hubs) you can connect 54 Thunderbolt devices ((3^3)x(5-3))
With 4 levels of hubs (1+3+9+27 hubs) you can connect 81 Thunderbolt devices ((3^4)x(5-4))
That's theoretical. I haven't seen anyone test if chaining hubs together actually works.
Plus, there's a limited amount of PCI resources. For example, there's only 255 PCI buses. Each Thunderbolt device takes a handful of PCI buses. A hub takes 4 so there's no way you can connect 40 of them (unless you have some code to remove the unused bus of the hub).
An M1 Mac allows at least 128 PCI buses per Thunderbolt port (each port is a separate PCI domain). Intel Macs allow fewer because all the Thunderbolt ports are on the same PCI domain and there are other PCI devices on the same domain (max buses per port = (255 - buses for built-in devices)÷number of Thunderbolt ports)
In any case, no matter how many docks you chain together, only a max of two displays can be supported from a single Thunderbolt port.
A Thunderbolt 4 hub uses the Goshen Ridge Thunderbolt controller.
1) One bus is for the upstream PCIe bridge of the Goshen Ridge Thunderbolt controller.
2) The upstream PCIe bridge has a bus for its downstream PCIe bridges (five downstream PCIe bridges).
3) One of the downstream PCIe bridges (device 00) has a bus for the USB controller in the Goshen Ridge (maybe M1 Mac doesn't use the USB controller because it supports USB4/Thunderbolt 4 USB tunnelling which bypasses the USB controller)
4) One of the downstream PCIe bridges (device 04) has a bus for the PCIe 3.0 x1 connection but this is unused in most Thunderbolt 4 devices.
5) The remaining three downstream PCIe bridges (devices 01,02,03) are for the downstream Thunderbolt ports which will each have a bus for the upstream PCIe bridge of the connected Thunderbolt device.
So at a minimum, a hub requires 2 buses (in the case of M1 Macs when the USB controller in the hub is unused) or 3 buses (in the case of Thunderbolt 3 Macs) but macOS will probably enumerate 4 buses for each unless a method is used to skip the unused buses.
For example, on my Mac mini 2018, a Thunderbolt 4 hub uses 7 buses.
- One for the upstream PCIe bridge
- One for the downstream PCIe bridge
- One for the USB controller
- Three for the downstream Thunderbolt ports - but I don't count these because they would be used by the upstream of the next Thunderbolt device.
- One for the PCIe 3.0 x1 link