What Makes a Game Old-School?

Paul Melroy over at the Emergence Campaign Weblog has an interesting series of three posts that do an excellent job of explaining what makes a game "old school"? He is working on a way to use the variant D20 system "Eclipse: The Codex Persona" to run a "old school" style game. I have my doubts that this would work for me, but these three posts tell me that Paul at least has a very good grasp of what makes a RPG "old school" (and why) and does an excellent job of explaining this.

• Old School Renaissance Eclipse Part I – Simulationism
• Old School Renaissance Eclipse Part II – Simplicity and the Roll of Last Resort
• Old School Renaissance Eclipse Part III – Creation and Consequences