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Re: Powerbook 12" USB power

On Mon, Sep 12, 2005 at 01:49:28PM +0200, Matthias Grimm wrote:
> On Mon, 12 Sep 2005 11:04:25 +0200
> "Federico 'Pain' Pistono" <fppain@gmail.com> wrote:
> > For some reasons my 12" Powerbook does not provide enough energy to
> > the USB device.
> > 
> > I have an external hard-drive, 80 GB USB 2.0, that has two connecting
> > cables. It usually works fine with just the connection cable on a
> > desktop with a USB 2, but if you have only a USB 1 or you have a
> > particular situation you can use the other cable as well, its purpose
> > is solely to provide energy when needed.
> >  
> > When I first used the powerbook on OSX it worked fine with just a
> > cable, and the same with Linux. Now it's gradually getting worse, and
> > I can't even transfer decently any file. I am sure thr USB 2 works and
> > it's configured, since if I plug the energy cable into another
> > computer and the connecting cable in my 12" it works fine, meaning
> > that I just nedd to provide more energy from my USB ports.
> Be carefull with that. USB is specified for 5V/500mA = 2.5W per
> Port/Hub. Most hard disks, even the 2.5" Laptop ones, use more power so
> you may damage your laptop if you use an external hard drive without
> external power supply. Read the datasheet of your hard drive carefully.
> Some time ago I replaced my internal hard drive with a bigger 40GB one.
> This hard disk has a nominal power consumption of 2.5W (USB limits) but
> needs 5W during power up sequence. I put the old one in an external USB
> housing. This hard disk has 2.5W nominal power consumtion and also 2.5W
> during power up sequence, but nevertheless I don't have the courage to
> use it without external power supply at my PowerBook.

Hehe, i got a nice usb+firewire 2.5" housing which had 2 usb connectors, one
for dat transfer, and the second plugged into the power adapter of the
housing, so you get the 5W you need for that :)

I am using it as firewire disk anyway though, so ...


Sven Luther

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