What must RAM sticks be compatible with?

RAM sticks must be compatible with the pins on the motherboard RAM slots because the physical design and arrangement of the pins are crucial for establishing a connection between the RAM and the motherboard. Every type of RAM, like DDR4 or DDR5, has a specific pin layout and notch placement that ensures it fits only in corresponding slots on the motherboard. If the pins do not match, the RAM will not physically install into the motherboard's RAM slots, rendering it unusable regardless of other specifications such as clock speed or capacity.

While the processor type, operating system, and size of the computer case may influence other components within a computer system, they do not directly determine whether a RAM stick can be installed. The processor can take advantage of different types and speeds of RAM depending on its design, but if the RAM doesn't fit the motherboard slots due to pin incompatibility, it won't be operable. Hence, compatibility with the motherboard's RAM slots is the most immediate requirement for successful RAM installation.