Asus P5N-VM WS - Manual (Page 32)

The memory modules may require a better cooling system to work stably under
full loading (4 DIMMs) setting.
2.4.2 Memory configurations
You may install 512 MB, 1 GB, and 2 GB non-ECC, unbuffered DDR2 DIMMs into
the DIMM sockets.
• You may install varying memory sizes in Channel A and Channel B. The
system maps the total size of the lower-sized channel for the dual-channel
configuration. Any excess memory from the higher-sized channel is then
mapped for single-channel operation.
• Always install DIMMs with the same CAS latency. For optimum
compatibility, it is recommended that you obtain memory modules from the
same vendor.
• Due to the memory address limitation on 32-bit Windows OS, when you
install 4GB or more memory on the motherboard, the actual usable memory
for the OS can be about 3GB or less. For effective use of memory, we
recommend that you install a 64-bit Windows OS when having 4GB or more
memory installed on the motherboard.
• This motherboard does not support memory modules made up of 128 Mb
chips.
2-12 Chapter 2: Hardware information