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My brother-in-law bought a 10 port active USB hub and connected it to his iMac(it's couple of years old). Over the course of about a week he noticed that his computer's performance has slowed quite a bit and was becoming quite bothersome.

He had one HD and a printer(usually off) connected to his hub. He has an external Time Machine drive connected directly to the iMac. His keyboard is connected directly to his iMac

For example, browsers were slow, shutting down and putting the computer to sleep took minutes, Time Machine just chugged and didn't work well. So he turned off time machine and the computer was still slow.

When we disconnected the hub, things were zippy again! I suspected that it may have been Spotlight trying to catalog the drives. Connected the Time Machine drive directly again. Things still worked fine.

Next things to try:

  • Just connecting the hub without any devices
  • reconnecting the drives to the hub

I the meantime, has anyone ever experienced a performance degradation from connecting devices via a USB hub?

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