Interesting find M3Max USB-C has power fluctuation protection

[jlc1978]

I git a multi-drive adapter for SD cards, CF, etc. and plugged it into my MBP M3Max USB-C port and it didn't work. Tried different ports, restart and no joy. Decided to test on an M1 Air and it worked. Turned out it tripped the M3 Max's power protection, which other chips appear not to have. Plugged it into my powered hub and the MBP recognized it.

 

[benholt]

Same story here with a Sabrent SD/CF/microSD combo reader on the 16" M3 Max — dead port until I put it behind a self-powered CalDigit hub, but the exact same reader worked bare on the 2015 Air. Best guess is the multi-slot readers spike inrush past the M3's USB4 controller budget at enumeration and the port controller just cuts hard instead of brown-outing like the older USB-C 3.1 Gen 2 lines did. Anything with more than one bridge chip inside is basically a candidate for a powered hub now.