[olug] Firewire PCI cards

Ryan O'Rourke ryano at ch-gifts.com
Thu May 13 19:42:36 UTC 2004

On Thu, 2004-05-13 at 14:24, Phil Brutsche wrote:
> Ryan O'Rourke wrote:
> > I'm buying one of those combo Firewire and USB 2.0 PCI cards this
> > weekend so I can start video conferencing with a webcam. I've found a
> > couple models to choose from that seem to work well with Linux, but I'm
> > wondering about speed issues. How much bandwidth does the PCI bus have?
> > I thought it was around 132 MB/sec.
> For a 32-bit 33MHz bus it can burst transfers at that rate.
> For real-world usage you're lucky if it'll be 60% or 70% of that.  The 
> quality of the motherboard as well as the PCI chipset have a big impact 
> on your actual transfer rate.
>  > What good is something as fast as
> > IEEE 1394 or USB 2.0 if it's limited by the PCI card itself?
> Even if the cards are limited by your PCI bandwidth, USB 2.0 will still 
> provide better performance than USB 1.1 (which is 12Mbit IIRC), provided 
> you are using USB 2.0 peripherals.

So in reality, even if I have a Firewire or USB 2.0 webcam, it's still
going to only run at 90MB/sec if it's plugged into the PCI card.
Does anyone have any real world experience with trying to do quality
(true 640x480, 30fps, plus voice) video conferencing on a Firewire PCI
card like this?

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