.13 means it draws less power and emits less heat than .18 or anything larger. So a AMD AthlonXP 2000+(.18u) would have less overclocking ability than a AMD AthlonXP 2000+(.13u), as the .13 is much newer and the smaller die has more heat headroom. But as far as performance goes straight up, they should be the same, though Id upgrade to a more recent mobo if I were you anyway.