BIOS not detecting all memory

My system (Azza motherboard model 5VMD, VIA MVP3) will not read more than 196 MB of RAM even though I have 256 MB installed. Each stick will read the full 128 MB if I put them in by themselves. But if I have both installed together, system only reads 196 MB. This happened with several different brands of RAM. I made sure that they are both 16×64, PC100 (1 stick is from Crucial, the other from KByte). The BIOS is Award v 4.51 PG, and it reports SDRAM 8 ns in 2 banks. Could it be a setting that’s off? Should I update the BIOS?