NVIDIA's nForce2 Part II: Diving Deeperby Anand Lal Shimpi on October 21, 2002 4:05 PM EST
- Posted in
Update on Networking
In our first nForce2 article we investigated the performance of NVIDIA's two integrated Ethernet MACs (Media Access Controllers); we concluded that the integrated NVIDIA MAC was an excellent high-performance Ethernet controller, able to rival even Intel's highly regarded PCI NICs.
However, in our tests we were not so pleased with the secondary 3Com MAC which is present in the more expensive MCP-T. We once again went to NVIDIA with our results and got a couple of responses to our problem:
1) The 3Com MAC and drivers are not as tuned for performance as the NVIDIA MAC was. This supports the idea that the main purpose of the 3Com MAC is to win over the corporate community with the 3Com brand name, NVIDIA could have just as easily outfitted MCP-T with two of their own controllers instead.
2) The motherboards that AMD sent out for the XP 2800+ launch were not in fact using final nForce2 silicon. The performance we saw was a result of the A02 rev of the nForce2 MCP-T, while the bug is fixed in A03. The performance of the 3Com MAC is virtually identical to the NVIDIA MAC in the bandwidth tests, although CPU utilization is still higher. We have an explanation for this below.
The A03 stepping of the NVIDIA MCP-T fixes the 3Com performance issues
We also got a listing of the differences between the NVIDIA and 3Com MACs directly from NVIDIA:
1) The 3Com MAC supports IP, TCP and UDP Checksum offloads while the NVIDIA MAC does not.
2) The 3Com drivers include diagnostics software for DOS and Windows (a huge plus with the corporate community) while the NVIDIA drivers do not have that functionality yet.
3) The NVIDIA MAC supports interrupt moderation resulting in lower CPU utilization, the 3Com MAC does not.