Saturday, February 3rd 2007
Sony has updated their PS3 firmware edition to 1.51, and requires the update the moment a user logs into the PlayStation Network. However, it doesn't really address any major issues (I'm not saying there are any), and it doesn't add functionality. When asked what 1.51 does compared to 1.5, Sony gave us a fine-worded answer.
Support for PLAYSTATION 3 format software titles has been expanded.This probably has something to do with backwards compatibility, or allows future games to work.Source: 1Up