It's easy to calculate the capacity of a memory module if you know the capacities of the chips on it. If there are eight 64Mbit chips, it's a 512Mbit module. However, because the capacity of a module is described in megabytes, not megabits, you have to convert bits to bytes. To do this, divide the number of bits by 8. There are two ways to increase the capacity of a module.
Manufacturers can stack chips on top of one another, or they can stack boards.
In some cases, the stacking is done internally at the chip manufacturing plant and can actually appear to be one chip. In other cases the chips are stacked externally. The example below shows two externally stacked chips. Example of externally stacked chips. With board stacking, a secondary board mounts onto the primary board, which fits into the memory socket on the system motherboard.