my ddr 400 mzh not all recognized

[tharunam]

I have a abit kv7-v motherboard. I installed 2gigs of ddr 400 mhz memory. when it is clocked at 256mzh it recognizes all 2gigs but at 400 mhz it only recognizes 1.5 gigs.

Please help me with the correct setting to get this resolved.

Thanks