I'm starting to investigate the drag that USB puts on computers. I first clued in when I read about the difference between external hard drives that use USB 2.0 or Firewire. USB is dreadful for external drives, because it puts the processing load on the host CPU; in contrast, FireWire offloads, and thus is more efficient. (That's one reason why FireWire drives cost a bit more.) Nearly all my external drives are FireWire.
USB is fine for printers, because typically your computer's CPU has to do all the work in generating the bitmap data for the printer anyhow. But I began two wonder when my kids were complaining about the slow speed of their computers and we couldn't find a cause...
In particular, my daughter's relatively notebook computer has been running very slowly. It can take minutes for an app to load. I checked for common problems, but found none: (1) disk still 50% free; (2) no viruses and so on; (3) CPU utilization was less than 10%; (4) hard drive was not being accessed excessively; (5) no apps running in the background.
The sole difference seemed to be whether a USB card reader was plugged in. Later, when she removed it, the computer seemed faster to her.
I had noticed a similar problem with my desktop computer. I recently moved the keyboard from the PS/2 port to a USB port. I noticed that the keyboard ran slower; for a high-speed touch typist, like me, this is an issue. It's easy to show: open a word processing document, and hold down any key, like "A". The stream of As should be continuous; but when the keyboard was plugged into USB, the As came in bursts. A half-dozen As, then a pause, and so on.
As well, functions were disabled on this keyboard. The volume control and horizontal scroll no longer worked. This morning, I moved the keyboard's plug back to the PS/2 port, and it's working properly again.
These events led me to wonder just how much of our computers' slowdown is due to the many USB devices we have plugged into our computers, each one demanding some CPU time for itself.
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