In message <drr6mn$lhl$1@otis.netspace.net.au>, RoyB
<roy@rbdb.?.removespamjunk.net.invalid> writes
>I have an external laptop HD in one of those neat USB cases. MB is a
>Gigabyte 8IRXP.
>
>When connected to the USB2 ports on the rear panel the device correctly
>powers up via the USB port VCC.
>
>When connected to an added USB port via the mainboard jack it works but only
>if I provide external power. Wiring to mainboard USB jack is correct -
>checked, rechecked and re-rechecked.
>
>Anyone else seen this problem or - better yet, have a solution?
>
>
>
Not specifically on that board, but I have very similar problems with an
add in USB board and a secondary (powered) hub.
Plug a hard drive into the add in board rear ports - works fine, plug in
to an external powered hub - fails!!
My diagnosis is that the "over current" protection for the USB port in
the external hub has a lower setting (tolerance around 500ma nominal?)
than the add-in USB Board, and that the external hard drive (rated at
500ma) just exceeds it.
I can only suggest
a) External power
b) A different added USB port unit ( the tolerances may be different)
A word of warning. I had an external drive "fail" under these conditions
that needed me to install the failed external drive as an internal and
perform low level formatting to recover it.
--
Peter R Cook
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