I have a P4 1.4 GHz system with 128 MB (64MB x2) of RDRAM on Intels i850 chipset based motherboard . Now I want to upgrade my memory to about 256 MB. I have heard that you have to always fit an identical pair of RDRAM chips. I have 2 RIMM slots fitted with some kind of dummy chips Can I replace just one of them with 128 MB or do I have to get a pair of 128 MB chips ?