Compaq AlphaServer GS140 Getting Started page 27

When you are defining three partitions, three memory modules are always
needed. They may or may not be of the same size. Figure 2–5 shows some
examples of how memory is divided in this case.
When all three memories are of the same size, one is allocated to each partition.
When the memories are of different size, the largest memory is assigned to
partition 0; the next largest (or equal), to partition 1, and the next largest (or
equal), to partition 2.
Again, set the interleave environment variable to none, as noted in Chapter 4.
Configuration Rules 2-11