A.Install more cards of smaller capacity and same size across MCMs. Use DDR2(dual data rate) memory if using HPC (High Performance Computing). 
B.Install fewer cards of larger capacity of the same size across MCMs. Servers with one processor book must have a minimum of four memory cards installed. 
C.Intermix DDR1 and DDR2 memory so that partitions requiring the higher performance can take advantage of them. Half of the available memory slots in the system should contain memory. 
D.Use fewer higher density memory cards so that a few memory slots are left open for future growth. Each processor book provides sixteen memory card slots. The p5 590 supports a maximum of 64 memory cards.

A.pSeries eWLM can create classes while pSeries WLM can create tiers.
B.pSeries eWLM can create  tiers while pSeries WLM can create classes.
C.pSeries eWLM is implemented over multiple O/S images while pSeries WLM is implemented within an individual O/S image.
D.pSeries eWLM is implemented within an individual O/S image while pSeries WLM is implemented over multiple O/S images.