DDR3 Memory ranks -- Doubts

In TK1, the memory controller has 2 channels and each channel has 2 chip selects.
In Jetson TK1 reference board, DDR3 may be 164 configuration and from DDR3 controller,
4 chip selects are connected to 4 memory devices. This memory device width is 16, then
we achieves 16
4=64bit memory.

In this system, in DDR3 memory, how many ranks are here. How we are calculating the memory ranks.
Whether this memory is 4 rank X16 configuration or 1 rank configuration?
It should be a 1 rank configuration. Need to confirm this.

Thanks for the reply.

Yes, Jetson TK1 board is 1 rank x64 configuration, you can calculate ranks by data lines number and address lines setting.