Asus RS500A-X6/PS4 - Manual (Page 26)

Chapter 2: Hardware setup 2-8
2.3.2 Memory Configurations
You may install 1 GB, 2 GB, 4 GB, or 8GB registered ECC/unbuffered ECC DDR3
DIMMs into the DIMM sockets using the memory configurations in this section.
Always install DIMMs with the same CAS latency. For optimum compatibility, it
is recommended that you obtain memory modules from the same vendor.
Memory population table
SR: Single Rank; DR: Double Rank; QR: Quad Rank
DIMM0 DIMM1 DIMM2 Max MHz (1.5V) Max MHz (1.35V) Timing Mode
UDIMM -- -- SR/DR 800 800 1T
SR/DR -- SR/DR 800 800 1T
-- -- SR/DR 1066 1066 1T
SR/DR -- SR/DR 1066 1066 1T
-- -- SR/DR 1333 1333 1T
SR -- SR 1333 1333 2T
DR -- DR 1333 -- 2T
SR -- DR 1333 -- 2T
DR -- SR 1333 -- 2T
RDIMM -- -- SR/DR 667 667
SR/DR -- SR/DR 667 667
-- QR SR/DR 667 667
SR/DR SR/DR SR/DR 667 667
SR/DR QR SR/DR 667 667
-- -- SR/DR 800 800
SR/DR -- SR/DR 800 800
-- QR SR/DR 800 --
SR/DR SR/DR SR/DR 800 800
-- QR -- 800 800
-- -- SR/DR 1066 1066
SR/DR -- SR/DR 1066 1066
SR SR SR 1066 --
-- -- SR/DR 1333 1333
SR -- SR 1333 1333
DO NOT install DIMMs of different voltages on the motherboard at the same
time, such as a combination of 1.5V DIMMs and 1.35V LVDIMMs.