RIMM reporting less memory

My PCP4 with Intel 850GB MOBO and PC800 RIMM 64*2slots and CRIMM on the 2 slots
on POST checks reports only 88 MB of RAM instead of 128 MB. It says mem size reduced.
Why? How it can be rectifed? Otherwise the PC runs OK
I tried with filling the other slots 64MB*2slots also reports the 40MB less only.
One particular mem chip reports like that.
Is there any way to solve it?