Can wince 4.2 address 256mb RAM on netBook Pro

I'm running CE4.2 on the nbpro Psion Lx motherboard. The O/S in system settings show 40mb available on the flash disc instead of 10mb but still show only 80mb available on RAM. Settings propeties shows the 256mb ram.

Is there a registry setting I can adjust to allow the o/s to take advantage of the extra ram.

Allan