# Firewire 1 vs. USB 2.0 comment.



## zigzagry (Apr 12, 2003)

I have never really had a need for either of these until recently. But I always wonderd what was actually faster.

firewire being ratd at 400 mb/s
usb 2.0 at 480 mb/s

All the pc lovers at work tell me how firewire is useless now that usb 2.0 has come along because the usb 2 is faster. I would not agree with them no matter what the rating said, and now I'm able to try it out for myself.

I bought an external firewire/usb 2.0 HD case about a week ago. While transfering files I decided that It would be a good Idea to test out the speeds of each. Here are my results.

(tests done with a dual 450 g4. Stock firewire ports, and a usb 2.0 pci card)

• file tranfers done using a 4.2 gb file from one western digital 80gb, 7200 rpm, 8 mb cache. To another drive with the same specs.

• transfering the file using firewire took about 4.5 min.

• USB 2.0 was more than 6 minutes.

does anybody find USB 2.0 to be faster than firewire?

I'm gonna do some more tests this weekend. So far I am very happy with firewire though.


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## wonderings (Jun 10, 2003)

I thought I heard that USB 2.0 was only able to reach that speed, but varried, where as Firewire was constant. I could be wrong though, just something I thought I heard somewhere.


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## ArtistSeries (Nov 8, 2004)

The mac implementation of USB 2.0 is slower than FW 400 on the Mac. I'm not sure of the reason.

On the PC side, MS has done a good job with USB 2.0 and it is fast for them...

USB does requires the processors to manage the data and firewire is mostly from the FW chip.


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## mikelr (Sep 6, 2004)

I find firewire much faster
forget usb 2 its not very fast


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## used to be jwoodget (Aug 22, 2002)

USB2 is THEORETICALLY faster than FW400 but in practice it is usually 20-30% slower (on PCs or Macs). Add to this the need to keep USB2 devices away from older USB1.1 devices (otherwise the former will drop to the latter speeds) and USB becomes a pain. The mixed standard problem can be avoided by using different hubs.

FW800 is a bit of a disappointment and will probably fade from view. Initial implementations of the 922 chipset only boosted throughput by 50% although newer chipsets do double the transfer rates. FW1600 and FW3200, although proposed, will not see the light of day. The future is in SATA links since these currently run at FW1600 speeds and emerging controllers run at the equivalence of FW3200. 

FW400 isn't going away thanks to the plethora of CE devices that use it. USB2 is fine as a peripheral controller but the future for it is also bleak given that wireless interconnects will likely take over from USBs traditional roles. But thats the way it is for I/O standards. They rarely seem to last more than a decade......

If you have a USB2/FW400 device, its best to use the FW connector (it also provides greater voltage).

For more information, check out the Wiebe Tech white papers.


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## zigzagry (Apr 12, 2003)

we just got a new 60" solvent printer and its FW.

nice to see firewire in at least one of our windows machines


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## Terry O'Leary (Jul 21, 2003)

There is more to the standards than just speed. USB 1.1 (and probably 2.0) devices require one device to be the host. The computer fills that role. But Firewire was made with the idea that peer to peer sharing of information can be done. I.E. you could have two firewire devices connected to your computer with the two devices passing info back and forth without bothering the computer.

One other thing that firewire allows is info flowing from one to many devices. So you could have a MiniDV camera sending info to many computers. I.E. a company could transmit live corporate video to many computers.

Now any particular firewire device may not have been built to take advantage of the two aspects of firewire I have outlined.

- Terry O'Leary


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## vectra (Jan 23, 2003)

I would like to thank gordguide for a great explanation!
Thanks!


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## gordguide (Jan 13, 2001)

Terry basically has it right; Firewire is a 400 speed peer-to-peer protocol while USB is a 480 speed master-slave protocol.

As long as you only have one device on the bus, USB 2 can beat Firewire by a nominal amount, provided the CPU is not busy with other applications/tasks and the controller chip is working properly. USB must use up CPU cycles to work; it can't work on it's own; USB devices have polling "overhead" where no data transfer takes place while it decides who to give the bus to next, or if anyone even needs the bus at all.

Firewire works without any intervention from the host computer at all; in fact 2 firewire devices can connect to each other (no computer at all) and still work at maximum efficiency. Also, the bus is shared in such a way that whomever needs it gets it and gets it's share cooperatively and dynamically (constantly changing); if both need it they get all they can use up to half of the bus; or more if the second doesn't need it's half, or all for one and none for the other, and so on. Each to his needs, each to his ability, and each can vary at any time.

If you look at USB 2 vs Firewire reviews, in every case it's a single device connected to a CPU in a "controlled test" which is another way of saying there are no applications running (sometimes one application only which is part of the test suite) and the computer is not communicating with a network, or what have you.

Under these conditions USB 2 can outperform Firewire marginally. However, I never use my computer like that; there are always a multitude of things going on at once.

Connect 2 devices on the chain, (no-one reviews like that) and USB slows down much more than Firewire. Run a bunch of applications or have the computer connected to an active network, and now the demand on CPU cycles begin to affect performance further.

None of these factors would affect Firewire, no matter how many devices were on the chain. Only the needs of each Firewire device itself affect data rates on a given device in the chain; if a drive needs 100% of 400 for a brief period and no other device objects, it gets 100%. If each demands 100%, they both get 50%, and so on.

USB 2 is better than USB 1.1, the specification for 1.1 limits the maximum speed of any single device to a bit less than 50% of the bus maximum if 2 or more devices are connected. I don't remember what USB 2 has (I have read the specification, but it was a while ago and it's about 100 pages of obscure technical stuff) but I believe it allows one device to have something like 80% of 480 if 2 or more devices are connected. What if 2 devices want that 80%? One has to wait until the first is good and ready to give the bus up or the controller acts like a traffic cop and forces things (CPU load will go near 100% for that little scrap).

CPU cycles and polling overhead increase with each added USB device, and the more devices connected, the more the traffic cop has to intervene. Firewire stays the same, at zero overhead, no matter how many devices are connected.

The maximum Bus voltage and current is also higher with Firewire; both are more than twice USB 2's limit. This can become critical with live recording or video work, for example.

Because USB is a controller/CPU dependent master/slave type bus, it is possible to badly behaving devices to "own" the bus and refuse to hand it off to others who clamor for some bandwidth. Not as rare as you might think; a badly behaving device will test better for throughput than it's nicely behaving competitors, so there is an incentive to create "bad USB citizens" who will apparently "win" competitive shootouts in reviews.

Most USB scanners seem to be pretty nasty this way, incidentally. They tend to hog not only the bus but also demand a lot of the CPU and controller as well. Oh, and they often come with crappy drivers, which doesn't help.

The short answer: if money is tight and you don't have demanding needs, say just one device, USB 2 is fine. If you use or plan to use multiple devices such as a scanner, a printer, an external drive or do CPU intensive stuff like capturing video or audio recording (where a few cycles borrowed will cause your recording to drop out) use FW as much as possible.

By the way, it's still a good idea to have USB1.1 around; keyboards and mice need virtually no bandwidth or power. If there are only USB 2 ports on your computer, be sure to use a separate channel for your 1.1 and 2 devices. If possible, have only the KB and mouse on one channel; it's a drag when USB problems with badly behaving peripherals kill your input devices (you will need to do a hard reboot).

[ November 12, 2004, 12:27 AM: Message edited by: gordguide ]


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