is the PS3 backwards compatible? can it play PS1 and PS2 games? I never did beat XII and I'd like to replay it. I'd also like to check out XIII just because I could say I've played it. the graphics are pretty nice, but I've heard mixed reviews on the battle system, story, and just the game in general...

I've read that there are specifics as to which unit will run PS2 discs. something to do with the GB of the unit purchased...? thought I would run the question here in case someone has experience.