How BIOS reports the type amd size of my memory

[logicman112]

I am writing an assembly program as a BIOS for ASUS, cusl2-c, Pentum III, 815/ICH2. and I want to read the type and size of each DIMM on the motherboard.
How can i do it? Is it done by reading some registers or it has a difficult sequence of code giving some commands to SMBus and for SPD ports?

 

[yeungl]

Is using CPU-z more easy?