What is MOESI?

MOESI is a way for computers to talk to each other clearly when they need to share things like toys or candies, but instead of toys and candies, they're sharing information.

Imagine you and your friend are playing with blocks. You both have copies of the same set of blocks, but sometimes one of you changes a block without telling the other. That can lead to confusion: when you look at your blocks, they don't match what your friend has. MOESI helps keep track of who has the most up-to-date version of each block, or in computer terms, it keeps track of memory states so computers know whether they need to update their copy or not.

MOESI stands for Modified, Occluded, Exclusive, Shared, and Invalid, these are the different states a block of memory can be in.

• If you're the only one using a block, it's Exclusive.
• If both of you are looking at the same block, it's Shared.
• If you change a copy, it becomes Modified.
• When one person changes something and the other doesn't know yet, it’s Occluded.
• And if a block has no valid information left, it’s Invalid.

MOESI helps make sure everyone in the game knows what's going on with their blocks, just like you'd know if your friend changed one of them!