@jaszy
A single DIMM can be quad rank. It doesn't matter how many single rank or dual rank DIMMs you install in a channel that will not magically make them quad rank. Interleaving memory access across channels or DIMMs within a channel is not the same as interleaving memory accesses within a single DIMM.
Here is an explanation of dual ranked, single ranked and quad ranked RAM, it has nothing to do with how many sticks you have installed (from a Fujitsu whitepaper on tuning performance with Intel Westmere CPU's in Primergy servers):
The number of ranks
The last table also shows that memory modules with 1, 2 or 4 ranks are available. This means: there are
DIMM with only one group of DRAM chips which synchronously read or write memory areas of width 64 bit.
The individual chip is responsible for 4 or 8 bit. Or there are two or four such groups. However, the DIMM
address and data lines are then common for both groups, i.e. only one of the groups can be active at any
given time. The motivation for dual and quad-rank DIMM is first the greater capacity, as can be seen in the
table.
A second advantage of dual and quad-rank modules is the physical reason already discussed. Memory cells
are arranged in two dimensions. A line is opened and then a column item is read in this line. While the line
(more commonly called page) is open, further column values can be read with a much lower latency. This
latency difference motivates optimization of the memory controller which reallocates the pending orders
regarding possible "open" memory pages. With dual and quad-rank modules, the probability of accessing an
open page increases.