Introduced in May 1994, the PowerBook 520 was the first PowerBook with '040 power. Blackbird is Apple's code name for a line of PowerBooks based on the 68LC040 processor. These PowerBooks introduce a full-sized keyboard (with 12 function keys), replace the trackball with a trackpad, have a 640x480 screen, and stereo speakers built into the lid. They are also designed so they can later be upgraded with a PowerPC processor.??These were a big hit since they were the first notebook computers from any manufacturer with any of these features: a trackpad, built-in Ethernet, 16-bit stereo sound, stereo speakers, an internal expansion bay, and auto-sleep when the lid is closed. The 520 has dual battery slots, allowing up to 4 hours from a charged pair of batteries and a 4-bit passive matrix display.