SiS 756: PCI Express for AMD Socket 939

Ethernet Performance

The new motherboard test suite, launched earlier this year, includes LAN performance measurements. The test procedure that we use was first described in a VIA white paper.

The Windows 2000 Driver Development Kit (DDK) includes a useful LAN testing utility called NTttcp. We used the NTttcp tool to test Ethernet throughput and the CPU utilization of the various Ethernet Controllers used on the various nForce4 and ATI motherboards. We did not test the ULi M1695/M1567 Ethernet controller since ULi only provides 10/100 performance on their LAN controller.

We set up one machine as the server; in this case, an Intel box with an Intel CSA Gigabit LAN connection. Intel CSA has a reputation for providing fast throughput and this seemed to be a reasonable choice to serve our Gigabit LAN clients. At the server side, we used the following Command Line as suggested by the VIA whitepaper on LAN testing:

NTttcps -m 4 ,0, -a 4 -l 256000 -n 30000

On the client side (the motherboard under test), we used the following Command Line:

NTttcpr - m 4 ,0, -a 4 - l 256000 - n 30000

At the conclusion of the test, we captured the throughput and CPU utilization figures from the client screen.

Earlier reviews have already measured the performance advantage of PCI Express Ethernet compared to PCI Ethernet in Gigabit LAN performance. The SiS 756/965L uses the SiS 901 Ethernet on the PCIe bus. The results clearly show that the SiS Gigabit Ethernet competes well with other PCI Express Gigabit Ethernet chips. Throughput is competitive with the best, but CPU utilization is among the highest that we have measured at around 56%.

Please keep in mind that CPU utilization measurements for Gigabit Ethernet can be somewhat misleading, since they measure the percentage of CPU tie-up at sustained Gigabit receiving. In reality, it would be very rare that you would actually see sustained Gigabit transmission levels on your PC. For that reason, you should put the measured CPU utilization of Gigabit PCIe LAN in perspective. It will almost always be much lower than what we have measured.