Back to the point, if your looking to overclock that socket A I had pretty good success with the Nforce 2 chipset. My personal favorite was the Shuttle AN35 Ultra, Abit NF-7 S, and my friends ASUS A7N8 (<3 Soundstorm). I had pretty good success with the Abit and Shuttle and reached 2.1 Ghz easily with an 1800+ Tbred B (similar to your sempron i think), and 2.4 Ghz with a 2200+ Mobile XP.

i'm going to upgrade my system so i leave this sempron to my father thx postale