It is most likely you have purchased RDIMM's  (8gb) which cannot be mixed with the current 2gb UDIMM's.    The system will not pass POST with them mixed. The server will support up to 24gb using 2gb UDIMM's and up to 192gb using RDIMM's.   Regards,
The company that I work for just recently purchased a second hand PowerEdge R610. I upgraded firmware on the RAID card and anything else I could find then we were planning to add 32GB of ram to the 8GB in the machine, for a total of 40GB. We ordered the same speed of ram and both the previous ram and the new ram are ECC. We have 4x8GB 1333MHz ECC chips and 4x2GB 1333MHz ECC chips. They are different brands. I tried to install them in optimized mode (8GB in slots A1, A2, B1, B2 & 2GB in slots A3, A4, B3, B4) and the machine refuses to post. With only the four 8GB chips it will boot just fine. Is there any reason why I cant install the 2GB chips with the 8Gb chips?
R610 memory... help?