sv266ad motherboard not seeing all ram

I read that the SV266ad motherboard supports up to 2 gigs of ram. Since there is 2 ddr slots, I purchased a 1gb stick of pc2100 ddr ram. When I install it, the bios only detects 512mb. I have updated the bios and tested ram in another computer. Still it says I have 512mb. Any ideas?
Thanks