I have tomato firmware. I have my router set to N only, I have a 150mbps link between my computer and router. My router is not connected to the internet, I have no firewall on. When using a wired connection i get 100% perfect performance, no drops. I have updated the firmware on my router and atheros 9285, swithced to N only connection, shut off wireless security, nothing seems to help.
My computer is about 25 feet away from my router, the door is always left open to that room, and the router is connected via wire to the xbox 360. This gave me the best performance but it still fluctuates. I am streaming OTA HDTV via windows media center on both the pc and xbox, and the performance graph keeps fluctuating up and down on both the xbox when I look at the graph, and it mirrors itself on my task manager networking speed on the pc.