datarate problems

I am attempting to transmit a 42 MB/s digital video stream from a Firewire camera over a dedicated point to point gigabit Ethernet connection.

We are currently just testing the point to point connection and are having problems generating enough throughput with the gigabit Ethernet connection.

Si-soft Sandra benchmarks indicate that 50 MB/s is achievable with our connection (cat 6 cable, jumbo packets, flow control on).

However we have been physically testing the link by transferring a large (1.5 GB) file and can only achieve approx 20 MB/s (25 - simplex and 20 / 12 duplex).

At present we have a 2800XP (shuttle) connected to a 2.4GHz Celeron, both with D-link DGE 530T Gigabit Ethernet cards and SATA raid 0 Hard drives.

At present the system is operating on the PCI bus (33 MHz x 32 bit I think???) and I know PCIe will allow higher data rates, but we require a compact motherboard and I have not found a compact PCIe (I also want to understand a bit more regarding the bottleneck we are encountering in the PCI setup)

Cheers