Performance of gigabit ethernet on PCI vs Northbridge

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Performance of gigabit ethernet on PCI vs Northbridge is an aspect of gigabit ethernet reviews that I've seen glossed over time and again. Of course it's nicer to offload as many hogs as possible from the PCI bus, but does that mean gigabit ethernet on the PCI bus is a lost cause?

Contents

Test Equipment

  • ASUS A8N-SLI Deluxe (on board gigabit ethernet)
  • Abit NF7-S V2.0 (NetGear GA311 gigabit PCI adapter)
  • ASUS A8N32-SLI Deluxe (on board gigabit ethernet)
  • NetGear GS105 5 port gigabit ethernet switch

Test Method

Ubuntu 5.10 Live discs were used on all three systems so as to be able to perform the following pair of commands; 

nc -l -p 27666 | wc -c



time cat /dev/zero | nc 192.168.0.1 27666

After executing the last command there for a period of time, I'd break the process and out would be spat a time on the client computer and a byte count on the serving computer. Periods tested were 10 and 40 seconds. Scores in the results are averages.

Test runs were done on both the NetGear switch and through cross over cables to see if there were any differences due to connection method.

Results

Over NetGear Switch (mbps)

Send/Recv A8N A8N32 NF7-S
A8N X 640.2 639.3
A8N32 640.1 X 630.3
NF7-S 580.2 582.8 X

Over Cross-over cable (mbps)

Send/Recv A8N A8N32 NF7-S
A8N X 620.1 618.7
A8N32 619.9 X 622.3
NF7-S 574.5 569.2 X

Conclusion

The PCI bus on a relatively new system did not seem to affect the performance of the gigabit connection other than sending throughput. The results do show that an inexpensive gigabit adapter chucked on the PCI bus will come very close to the speed of a northbridge connected gigabit ethernet solution. Some inefficiencies are to be expected from putting the card on the PCI bus but I think it would be a stretch to say that the PCI bus was a bottleneck.

Keeping in mind though, the NF7-S is a relatively modern motherboard and probably one of the last premium motherboards to have no onboard gigabit ethernet, and has a solid PCI bus implementation.

The NetGear GS105 switch also proved to be a solid performer here, consistently outperforming a crossover connection.

See also

Slow gigabit ethernet on VIA 686b southbridge based motherboard

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