View Full Version : Firewire/PCI bandwidth limits

June 3, 2006, 01:31:45
Dear TIS,

We are using two of your DFK 41BF02 cameras along with 2 Sony DFW910SX cameras (all cameras are 960x1280 color cameras). All four cameras are being control using the IC Imaging Control SDK. Our application only requires two cameras, although we are experimenting with trying to use data acquired with the 4 cameras. Each camera has it's own Firewire card and all cameras in this experiment are being triggered externally via a 4 to 5Hz pulse. We have fully optimized our capture and JPG encoding routines, and when the program is running, there still seems to be CPU cycles to spare and the hard drive speed should be fast enough to write down the imaging to disc.

The problem we are running into is that everything seems to work reasonably well when using 3 cameras, but we begin to lose a lot of images when we add the fourth camera. I realize there are limits imposed by the Firewire and PCI buses, but I don't really know how to go about calculating these.

Would you happen to have any insight into this, i.e. how do I calculate the PCI bus bandwith? Do you know of any cases where people are using this many cameras on one machine, and are there any tricks we could try to get better performance?

I appreciate any help in this matter.



Stefan Geissler
June 6, 2006, 15:25:15
Hi Brad,

Theoretically you have 132 MByte per second transfer rate. (33 Mhz * 4 Byte = 132.000.000 Bytes per second). Pratically there is some overhead for handshakes, protocoll data, headers etc. Also other devices like mouse, net work etc use their part of the transfer rate.
If you have four of your high resolution cameras connected to the computer, then you have in your configuration app. 50 MByte pro second transfer. This should work on your PC but it is not predictable, what other devices and processes need the PCI bus. Thus is suggest to remove all not needed hardware from the PC and check again. If this will advance your situation i do not know.