View Full Version : "Artificial" Firewire bandwidth limit?

August 7, 2008, 14:55:26
Dear Support:

I am trying to run multiple cameras with a single PCI-Express 4 port Firewire card that, in theory, should be able to handle four full-bandwidth Firewire 400 devices. Specifically, the adapter card description states:
"Compliant with IEEE 1394a-2000 Standard: Simultaneous operation of multiple high-performance devices.
1-Lane (x1) PCI-Express with transfer rate 2.5Gb/s full duplex channel."

However, while multiple *cards* allow multiple cameras, trying to put multiple cameras on the *same* card results in IC Capture 2.0 giving the standard bandwidth exceeded errors as per your table here http://www.theimagingsource.com/en/resources/whitepapers/download/fwcamsbandwwp.en.pdf, even though I don't see why this table should be applicable.

Is this some "artificial" CAM / IIDC limit, or a bug/feature in IC Capture, or a bug/feature in Windows XP SP2's driver for the firewire card, or...?

And if it is a bug/feature in IC Capture (though the error occurs even if I run multiple instances of IC capture, each with one camera...) , would the problem still exist in calls to your WDM driver from C++, or is it just an IC Capture *application* error?

Thanks much,

Sascha Schmidt
August 8, 2008, 09:51:35
Dear TechnoFrolics,

this is not a IC Capture/application or driver error.
There is no relation between the intern pci-express banwith of 2,5Gb/s and the firewire bandwidth outward.
It seems that your firewire card has only one firewire controller and is according to that limited to 400Mb/s.

August 8, 2008, 16:02:31
Dear Sascha:

Thank you for the response.

I did understand that the PCI bus bandwith was separate from the firewire 400 Mb/s limit, but the card seemed from all language to suggest it had 4 separate independent firewire controllers. I gather from your response that apparently it does not, and presumably just has misleading marketing language...

I looked on the web just now, but did not have any luck - you don't by chance happen to know of a PCI Express firewire with *true* multiple independent controllers, each with their own 400Mb/s bandwidth?


Stefan Geissler
August 25, 2008, 11:12:51

We are very sorry, but we a still searching on our own with no success.