Total power from USB

Tiago Marques tiagomnm at
Sat Apr 24 12:55:27 EDT 2010

Hi all,

I've ran into something on the 1.5 B2 I have here, which I'm in doubt if may
or may not be relevant for OLPC's hardware people(it seems not), so I'm
reporting it anyway.

All three USB ports can deliver enough power to an USB 2.5" HDD, no problem.
They cannot in the following conditions:

 - An extra SD card is plugged in
 - Another USB device is plugged in one port, even one of lower power like a
flash drive. (sometimes it only takes one, sometimes it takes two, SD card
power also seems to be an issue)

When I try to plug in the 2.5" HDD, it doesn't have enough power to spindle
at enough speed and sits there trying to start itself.
When plugging in an USB device or SD card after the 2.5" HDD is already
working, it suffers a loss of power and enters the restarting state. This is
true if the SD card is plugged in instead(with another USB device present),
which suggests me that the power is shared.
No other plugged devices seem to be rendered temporarily unaccessible due to
the power failure on the high power device.

Best regards,
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