TurkWebmaster,  The issue is due to the R710's memory speed policy, where as with single and dual ranked dimms then using three memory modules per channel will limit it to 800 MHz regardless of the memory module speed. The R610 doesn't have that policy, which is why it maintains the speed. If you go to 2 memory modules per channel it would free back up to 1333mHz.  You can read more about the memory speed policy on this link in section 7.3 [URL] Let me know if this answers your question. 
Hello, i have at the moment two R710 and one R610 servers. I have on all of the servers the same memory configuration. 32GB Registered Memories (4 x 8GB) The DIMM slot populations are as follows on all of them:A2, A3, B2, B3and the speed is on all of them 1333 MHz with Advanced ECC mode (the cpus are the same pair x5650). I wanted to upgrade the ram modules for the R610 Server 64GB (8 x 8GB in Advanced Mode) and for R710 Servers to 96GB (12 x 8GB in Advanced Mode).  On R610 Server if i populate the modules as follows:A2, A3, A5, A6 & B2, B3, B5, B6 in Advanced ECC Modethe speed is at 1333 MHz.But if i populate the modules on R710 Servers as follows:A2, A3, A5, A6, A8, A9 & B2, B3, B5, B6, B8, B9the speed is at 800 MHz.  In the technical guides it tells that "Three memory modules per channel are limited to 800 MHz". The speed should than correct for the R710 servers but altought in R610 Technical Guide it tells "Two memory modules per channel supports up to 1066 MHz" it has the speed at 1333 MHz. Why there is this difference, altought they have the same configuration.  Would someone help me on this conflict?  Best regards Murat
R710 & R610 same memory configuration but different speed