External HD with no external power?

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External hard drives (USB) always seem to need an external power
adapter. That's very clunky and hard to carry around.

Are there external hard drives that don't need external power?

I know that there are some drives that don't need an external power
adapter when plugged into *two* USB plugs at the computer. However,
that's not an option for me since my two USB plugs are at two
different sides of the laptops.

Is Firewire the way to go?


Re: External HD with no external power?

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Firewire is very slightly slower.

Re: External HD with no external power?

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Firewire is more than slightly faster (can be a third faster).  The fact
that the quoted bps figure (400 as opposed to 480 for USB2) is lower doesn't
actually tell you much.  Firewire has several features that actually make it
faster.  For a start it is a full duplex bus system (USB is half duplex).
Also Firewire can operate with minimal processor support (USB relies
entirely on processor support).

However, the firewire connector on a laptop rarely supplies power.

Re: External HD with no external power?

The basic premise is wrong.  External 2.5" USB hard drives most commonly
do not need external power.  [3.5" drives will always need it, and some
2.5" drives will also, but not all and perhaps not even most.]

The USB spec allows 500ma per USB port.  That is enough for many drives.
  Further, many USB ports on many computers (both laptop and desktop)
will actually supply more than 500ma anyway.  Frankly, I'd try a drive
even it said that it's power requirement was more than 500ma, because
there is a very good chance that it will work just fine (the heaviest
load is starting the platters turning when you first plug it in ... you
will know immediately if it's going to work or not).

Firewire won't help; the Firewire ports on laptops usually don't supply
power at all.

If you need to use two USB ports, get a USB "extension cord" to be able
to connect to both ports, or use an external power supply.

Markus Dehmann wrote:
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