Time to spend some money...
To test whether a laptop of more current design would eliminate this unbalance, we obtained a Dell Insprion 4100 with 1GHz Celeron CPU, 128MB of RAM, and running WinXP Home. Plot 2 shows the same test as Plot 1, but run with the Dell in place of the Compaq laptop. There's clearly still a send, receive imbalance, but the percentange differences are smaller, and average speeds are significantly higher. It's also interesting to note that the receive test has smaller variation in this case. Note also that in order to control the number of variables in the test, we used the Linksys adapter for this test, even though the Dell comes with a 10/100 adapter built in.
Plot 2: Dell laptop - Receive vs Send
To see if we could get a better feel for the relationship between processor speed and network throughput, we ran tests between three pairs of machines:
- "dell" is the previously described laptop (1GHz Celeron)
- "pat" is a Compaq Presario 5451 with 500MHz AMD-K6-2, 252MB RAM, Win98SE, and Netgear FA310TX PCI Fast Ethernet adapter
- "rat" is the previously described Compaq Deskpro (733MHz Pentium III)
The results shown in Plot 3 show that the pairing of 500 and 733MHz machines turn in the slowest performance. Next best is the 500 and 1GHz pairing, followed by the best performance via the matchup of 733MHz and 1GHz machines. Although it's surprising that it took two over-500MHz machines to get at least 50Mbps network throughput in both directions, we can't really say that these results represent a hard rule, given all the variables in the experiment. But it's clear that faster is better!