Thunderbolt Bridge speed is slow - help please

[pgseye]

I have an M2 Mac Studio and an M4 MBP, for which I would like to directly connect to transfer large files. I read that a Thunderbolt Bridge was one way to do that. I bought one of these cables directly from Apple as I know from experience that some third-party cables don't work the way they claim:

https://www.apple.com/au/shop/product/HRGZ2ZM/A/caldigit-thunderbolt-4-usb‑c-pro-cable-1m

When I connect the two Macs, I see a 'Self-assigned IP' connection with a yellow dot on both computers. The speed transfer seems to be limited to about 40 Mb/sec. Thunderbolt 4 should provide much faster speeds than that, right? Have I not set the network connection up correctly?

edit - looking under System Information -> Thunderbolt/USB4, I can see each computer connected to the other at their relevant ports with a suggested link speed of 40Gb/s

 

[joevt]

The problem might be the file systems?
Do an iperf test to test just the network speed between the Macs over Thunderbolt?

 

[pgseye]

The problem might be the file systems?
Do an iperf test to test just the network speed between the Macs over Thunderbolt?

Thank you - that is really helpful.

So I installed homebrew and then iperf and I get the following - which suggests the connection is in fact working at close to the link speed.

I am now beginning to think I am doing something sub-optimal in how I attempting to connect the two computers. I don't know much about networking, but I think have set up the connection in both Finder and Forklift using "smb" protocol. I wonder if that is the problem? If that is the problem, what is the best way to connect (and how do I do it)?

 

[pgseye]

I think I have figured this out now. I was connecting to the wrong IP address (facepalm). The connection now seems to work.

 

[joevt]

So I installed homebrew and then iperf and I get the following - which suggests the connection is in fact working at close to the link speed.

Wow, that's more than I expected. This may be a result of USB4 and improved drivers rather than older Thunderbolt 3 stuff.

I think I have figured this out now. I was connecting to the wrong IP address (facepalm). The connection now seems to work.

Can you get a benchmark for disk I/O over the Thunderbolt connection? Maybe AmorphousDiskMark.app?

 

[Fishrrman]

How "large" are the files you usually transfer?
Unless you're doing this constantly, wouldn't a fast USBc flash drive do almost as well?