[Tfug] USB 2.0 vs. firewire?

[Shawn Nock]

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Brian Masur wrote:

> Also, I thought OHCI was just certain vendors implementations of 
> USB, didn't think it had anything to do with firewire.

Did some checking:

OHCI sems to be the current buzzword for "standard controller software
interface". So an OHCI USB driver will drive any OHCI USB controller
regardless of manufacturer nothing else is implied but the driver <->
controller interface.

Intel thought that this was great except they didn't get any license
revenue. So UHCI is Intel branded OHCI with a slight performance hit
from implementation details and wallet shock from paying up for rights.

More info :
(Stolen shamelessly from Wikipedia; http://en.wikipedia.org/wiki/UHCI):

"At version 1.0 and 1.1 there were two competing HCD implementations.
Compaq's Open Host Controller Interface (OHCI) was adopted as the
standard by the USB-IF. However, Intel subsequently created a
specification they called the Universal Host Controller Interface (UHCI)
and insisted other implementers pay to license and implement UHCI. VIA
Technologies licensed the UHCI standard from Intel; all other chipset
implementers use OHCI. The main difference between OHCI and UHCI is the
fact that UHCI is more software-driven than OHCI is, making UHCI
slightly more processor-intensive but cheaper to implement (excluding
the license fees)."

(end quote)

The article downplays the speed difference between OHCI and UHCI in USB,
but seems to confirm my experience in USB2 v. Firewire:

"Despite all this and despite USB's theoretically higher speed, in real
life benchmarks the actual speed of FireWire hard drives nearly always
beats USB 2 hard drives by a significant margin (for example[7]). In
addition to this some operating systems take a conservative approach to
scheduling transactions and limit the number of transfers per frame,
reducing the maximum transfers from, say, the theoretical 13 per frame
to 10 or 9."

> Learn something every day.

The article is a very interesting read, I recommend it wholeheartedly.
It certainly cleared up some of my confusion on the issue. Also, the FW
v. USB argument is more double-sided in the article than I quoted it
(out of context).

Peace,
Shawn

- --
Shawn Nock (OpenPGP: 0xB64200E1)
Broadcast Engineer; KUAT Communications Group
University of Arizona
nock 'at ' arizona 'dot' edu
- --
"Despair leads to boredom, electronic games, computer hacking, poetry,
and other bad habits."  -Edward Abbey
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