I installed Windows XP 32bit on X9SCA with BIOS v1.0b, and the system would wake up from S5 by pressing PS/2 keyboard or mouse. Do you have fix for the problem?
Please update to the latest v1.1a BIOS on the website, it will fix the problem.
http://www.supermicro.com/products/motherboard/xeon/c202_c204/x9sca.cfm