
Memory Type: DDR3 PC3-8500, DDR3 (ECC)
Maximum Memory: 48GB
Slots: 6
Each memory slot can hold DDR3 PC3-8500 with a maximum of 4GB per slot.*
*Not to exceed manufacturer supported memory.

You cannot mix Registered and Unbuffered memory. If you use the Crucial 24GB Kit (CT1941102) all previous existing unbuffered memory must be removed.

Memory or DRAM is the 'working' memory of the computer. It's used to store data for programs (sequences of instructions) on a temporary basis.

video - installing memory