I've long wondered about that ...

This problem occurs (here and everywhere else I've tried long transfers) with numerous devices, but only those capable of long-term transfers, since bursts are bursts. Disk drive transfers are, of course, burst-based, and if you don't have long strings of high-rate transfers, via USB, you may not see this. However, I've observed that activity is frequently paused for long periods on USB devices, actually including disks. I use a moveable 1 TB USB drive to save the content of my network-accessible storage, every day, and often observe that there's no USB activity for 20-90 seconds at a time. I've always assumed that Windows was the problem. My systems, with a couple of exceptions, however, are all HP, Compaq, Dell, and Gateway, commercially built and equipped boxes, with nothing internally added and with the standard retail software minus the many many "rubbishware" programs meticulously stripped off.

Can you shed any light on what could cause this sort of pause on the USB transfers?