One other trap: "sides == ranks" is usually but not always true. For many generations of DRAM the default PCB layouts followed that rule, but it isn't universal. One thing that happens is that generation X memory is released, and single and double sided DRAM has 1 and 2 ranks. Then, higher density chips become available, and the same chips now fit on a single side but are still dual rank. Checking the sides is a good first check, but if you want to be absolutely sure you need a data sheet or to actually try and use it.