I have a Dimension 8100 with 384 mb of RDRAM and want to add another 512. Several years ago I upgraded from original 256 to current 384. The invoice for that upgrade stated that memory was NON ECC. I was led to beleive that any upgrades should be non ECC also.  According to tech specs for memory currently available from Dell memory is ECC. Can I mix the two or should I persue non ECC from sources other than Dell?