how to set value in ram bank on mb

i have a pIII 500 with 3 dimm slots (256k in slot 1, 128k in slot 3 and 128k in slot 3) on a 1440 bx/zx motherboard with no jumpers. bios (award modular bios 4.51pg) will not allow change in value for ram or slot.

system shows bank 1 set to 128k and banks 2-3 set to 64k, also shows 256k installed in slot 1, and 128k installed in slots 2-3.

boot up windows reads 384k ram. i have tried moving dimms but still can not get to 512k of ram.

need ideas on how to reset bank values for dimms to be 256, 128, 128 so windows will read all memory. (biostar and award web sites are no help and neither is the motherboard manual). all info on web says set valurs in bios…no can do unless i am missing something…duh?