Beekerc,

The R900 memory population rules are as follows;

All systems will include 4 Memory Risers

Supported configuration is a minimum of one DIMM in each riser

Memory must be populated beginning with DIMM Slot 1

Additional memory must be added sequentially beginning with Slot 2

DIMMs in the same number sockets in risers 1 & 2 or risers 3 & 4 must be the same

Identically numbered FBDIMM sockets for both memory boards must be populated with FBDIMMs identical in terms of timing, technology, and size. Example: DIMM A1 and B1 must be identical.

FBDIMMs installed in different socket positions (numbers) on a memory board can be different for dual-channel operation. Example: DIMMs A1 and B1 can be different from DIMMs A2 and B2.

Additional memory can be added by installing identical pairs of DIMMs in the lowest numbered available slots.

So to answer your question the pair would be riser A1 and B1, not 1 and 2 on riser A.

Let me know if this clarifies things.