How many USB devices is too many?

Question

How many USB devices is too many?

I have two USB hubs .. one 8-port and one 4-port. Both are powered and the 4-porter is chained from the 8-porter. Lately I've been noticing sporadic issues with my USB devices refusing to work. Am I overloading my bus? Do they sell hubs with more than 8 ports?

MacBook Pro, Mac OS X (10.5.5), 2.5 GHz 4GB 250GB

Posted on Nov 6, 2008 9:13 PM

Answer 1

Nov 7, 2008 4:31 AM in response to Craig Weiland

The maximum number of devices that can be connected to the computers USB port is 127 according to the USB specifications. That is not your problem. Your problem is likely related to mixing low and high speed devices on the same hub. High speed devices should only be connected to the first hub in the chain. Low speed devices should be connected to the second hub. The number of high speed devices that you have determines whether the first hub should be the 4 port or the 8 port hub. It would be best to not mix low and high speed devices at all. Put a hub on each of the MBPs USB ports and reserve one for low speed and the other for high speed.

Answer 2

Nov 9, 2008 9:10 AM in response to Retired Engineer

I hadn't thought of that. Hmm .. now I need to figure out which devices are high-speed and which aren't. I don't suppose there's a USB utility that will tell me that, is there? I'll do some checking.

I don't need 8 USB hubs. But I do have a lot of devices, including 2 external HDs (both of which want USB cables for data and power), an iPod, open port for a jump drive, flatbed scanner, Palm dock, digital camera dock, wireless mouse & keyboard and then the USB from my 20" Cinema Display and the smaller dock. Plus I also have devices that I don't use regularly but would still like to use, such as this and this.

Answer 3

Nov 10, 2008 12:24 AM in response to Craig Weiland

High Speed devices are for example External HDDs and pretty much anything that does data transfer, like iPod or an external DVD. Low speed are controllers, e.g keyboard, mouse, that joystick and multimedia controller you posted with the link.But best use both MBP ports and connect the hubs to them

Answer 4

sig

Level 8

35,912 points

Nov 7, 2008 2:02 AM in response to Craig Weiland

Check Belkin. What do you need 8 USB hubs for? Just asking.

Answer 5

JMF

Level 3

792 points

Nov 10, 2008 12:12 AM in response to Retired Engineer

Wow that is some interesting stuff. Now I wish I knew which of my things were high speed and which were low speed. I had no idea I could have 127 things connected 🙂