Is the ASRock 939Dual-SATA2 Socket 939 a good board?

Yup, pretty decent board, especially at that price. Nice that it also has 2 SATA ports and 1 SATA2 port. If I remember correctly there a few frequent users here that have this board and they like it.
 
A DOA can happen with anything. Of course some brands have more DOA's than others. Some Techspot members around here have the same board and are very happy with it.

Seems to be a great choice!
 
Back