Re: is Firewire 400 faster than USB 2.0?

In article <slrnig8996.kec.g.kreme@xxxxxxxxxxxxxx>,
Lewis <g.kreme@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

In message <idtm6o$ri2$1@xxxxxxxxxxxxxxxxxxxxx>
Bruce Esquibel <bje@xxxxxxxxx> wrote:
Jolly Roger <jollyroger@xxxxxxxxx> wrote:

One major draw-back for USB is that the slowest device on a USB bus
causes all other devices to communicate at that same slow speed.
Firewire doesn't have this limitation.


You or someone else mentioned this not too long ago and I don't think that
statement is true.

It is not emphatically true, but it is often true.

If you look at the system profile for a usb mouse, it shows the bus speed
at like "Up to 1.5 Mb/sec", a usb keyboard, "Up to 12 Mb/sec".

Yeah, Apple has good USB hardware.

So if you take a usb hub, plug in a usb keyboard, mouse and a hard drive,
the speed is going to be limited to 1.5Mb/sec on the drive?

Depends on the hub. Often, yes. I've had this exact problem with someone
who's USB2 hard drive was running at USB1 speeds.

There was probably some logic along these lines a long time ago with mixing
USB 1.0 and 2.0 hard drives on the same bus but I think what you might mean
is if you have a couple USB 2.0 drives on the same bus, the slower of the
two dictates overall throughput, but when copying from one to the other.

With USB there is no "one to the other" as everything goes through the
host computer. This is one of the ways that USB sucks compared to
Firewire.

But I'm pretty sure a copy from an internal drive (or on firewire) to either
one of the usb drives would be at the same speed as it would be if the other
drive not being copied to was disconnected.

Newere hubs are smarter, so if you have a USB1 device and a USB2 device
they will both run at full speed. Not at the same time though.

So if one USB drive is rated at 300mb/sec and the other at 200mb/sec, a
drive-to-drive copy between them would be 200mb/sec or less

A lot less.

but a copy from
an internal/fw drive to the 300mb/sec would still be 300mb/sec if the
200mb/sec drive was there or not.

It's presence on the bus doesn't slow down the faster drive unless the two
are copying back and forth to each other.

Depends on the hub.

Thanks to the both of you for the comments. I'll be sure to change my
statement accordingly - maybe something like:

"One major draw-back for USB is that in some circumstances (with some
USB hubs or hosts) the slowest device on a USB bus may cause other
devices on the same bus to communicate at that same slow speed. Firewire
doesn't have this limitation."

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