HP ML570 - ProLiant - G2 Manual page 15

If an application is already running, it may have already allocated and requested its
memory. In this situation, the application would need to be restarted (or some other
action taken) for it to begin taking advantage of the expanded memory. Other
applications that continuously request additional memory usually can take advantage
of the new memory without any user intervention.
NOTE: Some programs that report the total memory in a server (such as the System
Information Utility that comes with Microsoft Windows) do not include memory that has been
hot-added, although the memory is available and is being used by the OS.
16 HP ProLiant DL580 Generation 2 and HP ProLiant ML570 Generation 2 Server Hot-Add Memory