Hello,

I have a dual-processor PowerEdge R520, and I want to upgrade the memory, while retaining as many of my existing DIMMs as I can (all, preferably!). It currently has 32GB in 8x 4GB ECC DDR3 RDIMMs,1333MHz low volt single rank (Dell-331-4422). I'm looking at adding 2x 16GB ECC DDR3 RDIMMs, 1333 MHz  low-volt dual rank, PC3-10600. The R520 has three memory channels per processor, supporting up to 12 DIMMs I'm looking at the document ps2q09-20080414-Benson.pdf regarding Dell R520 memory configuration, but it's not clear to me how I should plan to configure the memory modules I have, or whether this upgrade is a good choice. Can I mix 16GB and 4GB DIMMs in the same channel? Which channel should use the larger DIMMs? Should I plan to purchase all new DIMMs if I want to increase the memory to 64GB? Can you advise?

Thanks!