Comment by Dylan16807

> Actually we're both wrong... it appears max length for a passive cable is 18 inches for full performance. Passive cables technically max out at 18 inches for 40gbps and drop to 20gbps at 2 meters. Past that you need an active cable (which has signal repeaters).

I'm still pretty sure it's based on signal loss, and the lengths are just estimates of what you can reliably get out of a cost-optimized manufacturing process.

> High-speed is half-duplex, yeah. It looks like SuperSpeed is full-duplex though so I'm wrong on that bit.

By "the high speed wires" I mean the pairs introduced with USB 3. Not USB's dumb naming conventions.

> I just remember it being a nightmare trying to use USB external hard drives (which would have been back in the USB 2.0/High-speed era when I used them last!) and reading/writing at the same time tanked performance far beyond what you'd get with even an internal HDD. Read or write, one at a time, mixing both was a trip to hell.

I think a big part of that is also the mass storage protocol combined with slow responses off a hard drive. I have a USB 2.0 SSD-class drive around here and it actually performs pretty well even on mixed workloads.