One connector, many headaches

What I ran into concerns the MacBook Pro 2018, 15" and the USB-C Digital AV Multiport Adapter (MJ1K2AM).

I was powering the laptop through the adapter (USB-C) while simultaneously having an external drive (WD Elements 1TB) in the USB-A port. The performance drop while working with photos was unlike anything I'd experienced — I was stitching panoramas in Adobe Lightroom. I don't have exact numbers, but we're talking tens of minutes per panorama (roughly 10 shots at 16 Mpix). That was puzzling because I was used to a somewhat different speed. I saved everything, backed up the catalogue, and plugged the power directly into the USB-C port on the laptop itself.

The performance difference was noticeable — instead of tens of minutes, the photo stitching took on the order of minutes. Explanation? I'll refer you to an article about USB-C published this year on cnews. I still don't fully understand it.

The conclusion is clear: never connect power through the adapter. What owners of 13" MacBooks are supposed to do, I have no idea — two ports is desperately little.

P.S. The new RPi4 is also powered via USB-C. You'd think you could use an adapter from a MacBook Pro? Wrong — a single resistor is to blame. The RPi developers have already addressed this bug, and newer revisions will be chargeable with "smart" adapters.