[olug] Firewire PCI cards

[Phil Brutsche]

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.

This, btw, is why:
  * modern servers typically have multiple PCI-X busses (100Mhz or 133MHz
    64-bit PCI)
  * PCI-E will be introduced in the next year or so
  * many modern motherboards have multiple PCI busses (seriously - the
    Dell Dimension 4600s I buy at work have separate busses for the PCI
    slots and the integrated devices

-- 

Phil Brutsche
phil at brutsche.us