Further Thunderbolt 4 Cable Testing

Any lingering thoughts I might have harbored that Thunderbolt 3 cables are essentially the same as Thunderbolt 4 cables were removed this morning. I decided to backup my iPad Pro to my Mac mini in addition to the regular iCloud backup. The only conveniently available port is a USB 3.0 hub stuck to the edge of my desktop and since the port on the iPad pro is USB type C I grabbed a Thunderbolt 3 from my drawer and plugged that into a USB type A to Type C adaptor and connected the iPad. The iPad chimed and indicated it was charging but did not connect. I rummaged through my collection of USB, Firewire, HDMI, Ethernet, and heaven only knows what other cables and found the Thunderbolt 4 certified cable I had forgotten I bought and replaced the Thunderbolt 3 cable with it. 🛎 bing! the iPad chimed, and appeared in the Finder sidebar. I have retested using other Thunderbolt 3 cables (all certified and all rated a 40Gb/s) with the same results.

CONCLUSIONS:
  • Thunderbolt 4 > Thunderbolt 3
  • Thunderbolt 3 ≨ Thunderbolt 4
  • Thunderbolt 4 is downward compatible with Thunderbolt 2, Thunderbolt 3, and all USB protocols with proper connection type adaptors
  • it is going to get expensive replacing all my Thunderbolt 3 cables with Thunderbolt 4
  • I have an excuse to clean out that rat's nest of outdated USB and Thunderbolt 3 cabling, hubs, etc.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein