Is PlayStation 3 backwards compatible

No most models have 2 USB ports and are not able to play PS2 games regardless of the harddrive size. All slim models can not play PS2 games and only about five million models were made that could play PS2 games worldwide

the old 20gb and the 60gb versions are the ONLY with the original emotion engine, which can NATIVITY run ps2 and ps1 games which means...20gb and 60gb's have the only 100% support for ps2 games and ps1. however the 4 usb port 80gb version is software emulation of the ps2 only and the same is true for all the Europe PS3 models with 4 USB ports.