Minecraft's 1.3 update is to launch on August 1st. The update will bring LAN support to single player games, new block types, and the ability to leave messages for other players in books.
But the update also brings an increase in system requirements. As Jeb explains on the Minecraft blog, " Since single-player has been turned into a shell on top of a background server, the game’s resource requirements have increased. When playing single-player, the game needs to be able to both simulate and emulate the world, which take many more CPU cycles. We’re working on optimizing rendering, but those improvements will not be included until Minecraft 1.4."
Spotted via VG247.