system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do CPU cores always come in even numbers?

For example, I've never seen a tri-core processor, or a penta-core, or a hepta-core. Is there a reason for this?
gpt
AMD Phenom processors were triple-core - the Phenom X3 series. The Xbox 360 also had a triple-core processor from IBM. Playstation 3 also used a processor with an unusual design - one main core and seven extra smaller cores.