Free Portal 2 "Peer Review" DLC hits October 4

Valve has announced the free DLC update for Portal 2 will be rolled out across all regions on Steam, Xbox Live and PSN starting October 4.

The free DLC, titled "Portal 2: Peer Review", is available to all owners of Portal 2 for download on PS3 and Xbox 360, and will be automatically downloaded via Steam on PC and Mac.

In it, you and a friend will continue the story of P-Body and Atlas as you traverse a new co-op test track and once again come into contact with GLaDOS.

The DLC also features a single player and co-op Challenge Mode, and leaderboards to compare Challenge Mode scores with friends and the Portal community.

To hold you over until the release next week, Valve has released the final installment of the Portal 2 soundtrack Music to Test By.