Cool I didn't know that about ps1 games. The first fat models could do ps2 hardware, and some fats after did software I think, but the slims to my understanding couldn't do it at all.
What I noticed was when I play a ps2 game bought from the store my slim reboots to play it. It got me thinking that they didn't port the game we are running ps2 games and it does software emulate after all. Why would the ps3 have to restart to launch it and then restart again to quit the game and return to XMB if the old ps2 game were truly compatible? Something's going on...