I've talked to 2 different people recently complaining that their wireless connection is faster than their wired connection. Both of them used Motorola modems.
Normally, I'd assume it's the computer. In one case, however, the user tried the same computer with both wired and wireless connections and found that the wired connection was consistently slow and the wireless connection was consistently fast. For both cases, we used speedtest.net to measure speed. How can I diagnose what's holding it back?
Case 1: Motorola SBG6580, DOCSIS3, built-in WiFi, 30 mbps
With the wireless connection, it tested around 30 mbps consistently. With the wired connection, it would max-out at 9.x mbps. We updated firmware on the modem and nothing changed. User didn't seem to mind.
Case 2: Motorola SB5101U, DOCSIS2, separate WiFi router, 15 mbps
Consistent 15 mbps over WiFi. Computer could only test with wired connection. He said it was an old computer, so I wanted to see if the Flash-based speed test was overwhelming the CPU. I had him open the Task Manager "Performance" tab while running the test. The CPU did not max-out. We noticed that the network card was running at 10 mbps link speed (this almost always negotiates 100m+ for most configurations). I walked him through the Device Manager and opened the properties for his network controller. We found that it was set to use 10m instead of auto-negotiate. We set it back to auto and restarted everything. The computer finally tested full-speed once or twice...but usually got poor speeds still.
The second case is probably just a problem with the PC. If that link speed setting was changed, a lot of other things might also be changed. I suggested he have someone look at it.
The first case is more interesting to me because we were able to test wired and wireless connections on the same computer. How would a guru diagnose the cause of this?