# Maximum USB ports

**URL:** <https://boards.straightdope.com/t/maximum-usb-ports/484268>\
**Category:** Factual Questions\
**Created:** [February 3, 2009, 4:52pm UTC](https://boards.straightdope.com/t/maximum-usb-ports/484268 "2009-02-03T16:52:44Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\
**Post date:** [February 3, 2009, 4:52pm UTC](https://boards.straightdope.com/t/maximum-usb-ports/484268/1 "2009-02-03T16:52:44Z")

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I have a 7-port USB hub, and need another port. Can I plug in a second 7-port hub into the computer? And if I ever need to . . . can I piggyback a new hub into my existing hub? What determines the number of USB ports a computer can handle?

If it matters, I have a G5 Mac.

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**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\
**Post date:** [February 3, 2009, 5:02pm UTC](https://boards.straightdope.com/t/maximum-usb-ports/484268/2 "2009-02-03T17:02:29Z")

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In using 7 port hubs be aware that some (check your specs) are actaully a split of 5 US 2.0 ports and 2 USB 1.1 ports.

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**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\
**Post date:** [February 3, 2009, 5:26pm UTC](https://boards.straightdope.com/t/maximum-usb-ports/484268/3 "2009-02-03T17:26:51Z")

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The maximum number of USB devices is 127 per host controller. A computer can have more than one host controller. Wiki explains it [here](http://en.wikipedia.org/wiki/USB).

And yes, you can daisy-chain hubs.

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**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\
**Post date:** [February 3, 2009, 9:57pm UTC](https://boards.straightdope.com/t/maximum-usb-ports/484268/4 "2009-02-03T21:57:59Z")

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> [@Quartz](#):
>
> And yes, you can daisy-chain hubs.

But speed will fall as devices share bandwidth.

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**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\
**Post date:** [February 3, 2009, 10:08pm UTC](https://boards.straightdope.com/t/maximum-usb-ports/484268/5 "2009-02-03T22:08:31Z")

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I believe it’s also true that devices on any root hub will be forced to drop to match the lowest-spec device, so a USB 1.1 memory stick would slow down transfer of data from a Hi-Speed USB 2.0 external drive, if they’re both plugged in at the same time.