AC66U 1 CPU maxes out at 10mbps DL on single thread, all other connections then drop

[dugaduga]

This is a relatively new phenomenon. Just added another router bumping the AC66u to gigabit speeds. If I download anything in a browser or application, it maxes out at 10mbps megabytes that is, then one router core maxes out, I can't open the WebUI or even a simple webpage in a browser. Even typing into Putty lags. Soon as I stop downloading, the cpu speed jumps back to 2-3%. What could be causing this?

I'm using the latest beta.

 

[dugaduga]

I've had some success tweaking my tcp stack and drivers in windows, congestion setting mods and whatnot this really seemed to help with the problems, however one core on the router is always at 100% simply downloading at 10 megabytes per second, even if its a single file and single thread / server connection. Seems a bit extreme.