1080p or 1680x1050

I changed my resolution on my xbox from 1080p to 1680x1050, and noticed although my display is slightly smaller, I have no jagged edges anywhere, while playing in 1080p everything was rough around the edges, why would this be when 1080p is supposed to be 1920x1080 resolution? this is on a 42" philips 1080p tv

consoles dont run most games in actual 1080P. The usually run in 720P and then are upscaled to be 1080P. Anytime on a computer you take a small image and blow it up things become more pixlated and thats what happening here. If the game was truly in 1080P it would look better but You do get mixed results with consoles because its not 1080P.

Were you using HDMI when connecting to the TV? or using the HD component cable?

I believe that may make a difference when viewing in 1080p (i could be wrong though)

I use HDMI, strange but the differences are huge from 1080p to 1680x1050, playing red dead redemption and everything is silky smooth, then I go back to 1080p and its jagged rough like theres no anti aliasing,

Ok - i thought that if you used HDMI the xbox only gives you a list of resolutions you can use (ie: 1080p, 1080i, 720p etc etc) - it doesn't give you a list of resolutions such as 1680 x 1050 etc....

are you forcing the TV to view at 1680 x 1050?

when I chose 1080p on my xbox - i check out the TV resolution and it tells me it is 1920 x 1080 running at 60Hz.....

(you could also be running the TV at 50Hz which may affect the picture....)