Why Do Some USB Cables Have Two USB Connectors at the End?
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Music by Eric Matyas
https://www.soundimage.org
Track title: Techno Intrigue Looping
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Chapters
00:00 Question
00:29 Accepted answer (Score 39)
01:11 Thank you
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Full question
https://superuser.com/questions/193966/w...
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Content licensed under CC BY-SA
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Tags
#harddrive #externalharddrive #usbstorage #usb2
#avk47
Become or hire the top 3% of the developers on Toptal https://topt.al/25cXVn
--------------------------------------------------
Music by Eric Matyas
https://www.soundimage.org
Track title: Techno Intrigue Looping
--
Chapters
00:00 Question
00:29 Accepted answer (Score 39)
01:11 Thank you
--
Full question
https://superuser.com/questions/193966/w...
--
Content licensed under CC BY-SA
https://meta.stackexchange.com/help/lice...
--
Tags
#harddrive #externalharddrive #usbstorage #usb2
#avk47
ACCEPTED ANSWER
Score 40
It's because of power consumption. There is a limit of how much power a single USB port can provide. It is measured in "unit loads" which are 100 mA for USB up to 2.0 and 150 mA for USB 3.0. A single port can provide at most 5 unit loads for USB 2.0 and 6 for USB 3.0, if there are no other devices connected. Some ports may provide more, but they aren't standard compliant and manufacturers can't rely on them. With two cables, device may use at least two unit loads, so it will have enough power to work.