h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Most "root hub" chips have two sockets, so for each two sockets you will have a total maximum of 480Mb/s. If you plug a "hub" into one of those sockets, the bandwidth is shared between all the devices attached as well as all those connected to the other socket on that "root hub".

The moral is - spread your high-bandwidth devices out around your "root hubs". Don't have two high bandwidth devices in a pair of sockets on the same root hub, rather pair each high bandwidth device (video grabber, HDD etc.) off with one or more low-bandwidth devices (keyboard, mouse, tablet etc.) and your system will be more responsive.

Again, for the purpose at hand the difference between Firewire and USB is not enough to be significant. But for the in all of us, the performance tests I've seen say firewire has better performance on Macs - they usually attribute that to the drivers since the same USB devices will be faster on PCs. For instance: http://www.choice.com.au/viewArticle.aspx?id=104527&catId=100533&tid=100008&p=3&title=FireWire+vs+Hi-Speed+USB

USB is cheaper. That's the important difference here. External power supply is cheaper too.

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As TiT says, using a bus-powered HDD on a battery operated laptop really limits you. You need an exceptionally low-power device, which in turn is likely to have a much smaller capacity. You should consider just moving files like movies etc. that you only use when you're sitting down somewhere onto the external drive and carrying a power supply.
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Sorry I didn't quite follow that. Are you saying that I need to get a drive with its own mains power supply, or that I can get a Bus powered one but try and use it when the laptop is on mains supply not on battery?

Part of the issue is that I am going to be living off grid a lot later this year and for the foreseeable future. I haven't figured out how much solar I am going to need to run the laptop yet, but was assuming it was manageable (because lots of people do it). But what I also need to know then is, which uses less power - to run a laptop and external drive off 2 power adaptors or to run the laptop off its power adaptor and the hdd off the laptop.

This is also an issue for my scanner which is Bus powered.

(I will probably have 240V supply)


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Bus Powered seems an easy choise, however concidering the hard drive will not be using more then 500mA the speed up and seek will be slow. If your USB can supply the 500 mA (many laptops are reduced to 250 mA to preserve battery power ? ). "
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When I have my scanner plugged in, the USB2 in the profiler shows this:

Bus Power (mA): 500
Speed: Up to 480 Mb/sec

Are you saying that the HDD needs more than 500mA? I can't find the specs for the lacie drive I am considering.

Traveller in Time nearly
"At least not both scanner and drive at the same time.

How about flash cards ? they will not give the full speed at writing but they are getting cheap and do consume nearly nothing. "

I won't be using the scanner and external hdd at the same time



I need 80GB+ for backing up. I assume flash cards aren't that big?

"I won't be using the scanner and external hdd at the same time"

Don't be so sure. When you're scanning in a detailed image it's common to scan at, say, 1200DPI and then despeckle and resample down to 300DPI or 200DPI. For that you need a lot of temporary drive space, which is exactly what your external drive will provide.