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Posted by Peter D on 01/20/08 16:10
Oh dear, where's the Geek to help you guys? :-)
OK, I'll be the Geek.
USB 2.0 (aka USB Hi-Speed) is technically faster (480Mbps) than Firewire 400
(400Mbps).
In real life USB maximum transfers peak at about 2/3 of that speed. If you
research actual test results, you'll often see speeds max out at 1/3 of the
max of 480 Mbps. Becasue USB creates a network where every device "chats'
with the central "host" (the computer in most cases) USB 2.0 requires more
CPU prcesses than Firewire and the more peripherals that are connected and
in use the slower the USB network. So avoid situations where you are
transferring from a USB device to a USB device (USB scanner to USB external
HD, USB camcorder to USB HD). Always transfer from a single USB device to a
non-USB device if possible. And don't forget that if you have a USB keyboard
and/or mouse connected you don't have a single device on the USB bus. Evbery
time you use the mouse or keyboard, you slow the network.
Firewire comes in two flavours. The original Firewire 400/IEEE1394(a) (100,
200, or 400 Mbps) and new Firewire 800/IEEE1394b (800Mbps). There's also a
'new' 3200 Mbps standard on the way. Actual speed is much closer to
technical speed, and faster and more reliable than USB. Why? Because of the
design. As well as significant design improvements that enhance and improve
efficiency through hardware implementation and control, Firewire allows each
device to control the network and each device can "speak" directly to
another without the need for a central "host". This significantly reduces
CPU load and increases transfer rates. Real life transfer rates on Firewire
are typically 90% of the max technical speed. Even poorly
configured/implemented Firewire can run at 80% of max speed.
Why Firewire is better than USB for Video:
As well as the significant real life speed improvement of Firewire over USB,
Firewire is also much better at sustained throughput, reducing (in fact in
most cases eliminating) dropped frames commonly seen in USB transfers.
A real test you can try:
Without doing anything else on the computer, transfer 5 minutes of video
using USB 2.0 and then Firewire and count the dropped frames. Now do it
again while using the computer (surf the net, type a letter, typical use
stuff). Now compare the droppped frames. I think you'll settle on Firewire.
Some sources:
http://en.wikipedia.org/wiki/USB
http://en.wikipedia.org/wiki/FireWire
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