Slots
This is the total number of memory upgrade slots (sockets) followed by their configuration. Banks are the way a system addresses memory. A bank must be completely filled with memory modules of the same size and type in order for the system to recognize and address the memory. i.e. :
3 (3 banks of 1) This indicates that there are 3 memory slots. These are divided into 3 banks, and each bank consists of one memory slot. So you can add memory one piece at a time for the system to use.

4 (2 banks of 2) This indicates that there are 4 memory slots. These are divided into 2 banks, and each bank consists of two memory slots. So you must add memory two pieces at a time (they must be the same size and type of memory) in order for the system to benefit from the upgrade.

12 (3 banks of 4) This indicates that there are 12 memory slots. These are divided into 3 banks, and each bank consists of four memory slots. So you must add memory four pieces at a time (and they must be the same size and type of memory) in order for the system to benefit from the upgrade.

4 Slot Vs 2 Slot Ram Upgrade

4 Slot Vs 2 Slot Ramsey

Most budget to midrange boards will either have two or four memory slots. I have a Gigabyte B450 DS3H with 4 memory slots and dual-channel support. If you have two slots and your motherboard supports dual-channel, setting it up is often as easy as just inserting a second memory module and booting up. Courtesy: GamersNexus. If you have 4 slots. Make sure if you have more than two slots the RAM is installed in slots of matching color – on a quad channel this is usually 1 & 3 or 2 & 4. If there is only one memory card and it is in the top slot, remove the top memory card before installing RAM in the bottom slot. Always install RAM in the slots from the bottom to the top. If you wanted 64gb of ram in 4 ram slots and you went with Samsung B-Die IC's or non-Micron, you'd get 16gb modules with memory IC's on both sides of all 4 dimms which equals 8 ranks since each dimm is dual ranked (512-bits). This could overload your CPU's Memory Controller, limiting your OC to your CPU AND your Memory. If you wanted 64gb of ram in 4 ram slots and you went with Samsung B-Die IC's or non-Micron, you'd get 16gb modules with memory IC's on both sides of all 4 dimms which equals 8 ranks since each dimm is dual ranked (512-bits). This could overload your CPU's Memory Controller, limiting your OC to your CPU AND your Memory.