Mac studio: which port is which bus for thunderbolt

For the the Max there are only 4 thunderbolt 4 ports and those are on the back. Each port is on a different bus. The two ports on the front of the Max are only USB-C. The two on the front of the Ultra are Thunderbolt ports but I do not know if those have separate buses.

The best way to check for the number of Thunderbolt buses and Thunderbolt devices, is to go to Apple > About this Mac > System Report > Hardware > Thunderbolt and look to see what Thunderbolt buses and devices are showing up.

Also note that only true Thunderbolt devices will register on the Thunderbolt Bus(es) and that all other USB devices, will only show up in the USB section.

Even though a non-thunderbolt device hooked up to a thunderbolt bus will not show the device under thunderbolt, it will list all ports and buses. I have the Max with no thunderbolt devices connected and it shows zero devices connected but lists the four TB buses, 0-3. I have other devices connected to two of the thunderbolt ports, one USB-C hub and one HDMI adapter.

The spec’s are at > Mac Studio - Technical Specifications - Apple