I have a brand new eTrex 32x. Connected via USB to a USB 3.0 port in Mass Storage mode. The transfer speeds are extremely (!) slow. It usually hovers around 500 KB/s or less. Just trying to backup the existing contents, the copying would have taken many hours.
Checked with USB Device Tree Viewer, and it says this:
Port maximum Speed : High-Speed (Companion Port 2-5 supports SuperSpeed) Device maximum Speed : Full-Speed Device Connection Speed : Full-Speed
and also
Device Bus Speed : 0x01 (Full-Speed)
Pretty sure this means it's running as USB 1.0, not even USB 2.0 (as that would be High-Speed). I tried the supplied USB cable as well as one of my own USB cables, and I tried 3 different USB ports. Always the exact same result. I also tried installing the Garmin USB drivers, though Windows doesn't seem to be using them (it uses Microsoft's WPD FileSystem Volume Driver).
The About section in Setup says the software version is 2.80. I bought this in Germany. I'm on Windows 10 Pro, on a B550 AMD chipset. The controller seems to be called "AMD USB 3.10 eXtensible Host Controller - 1.10 (Microsoft)" (idk if this means anything).
This connection speed seems completely unacceptable, surely this isn't how it's meant to be? I can't imagine trying to update maps this way. Just copying over 8 screenshots from the device onto my computer took like a minute.