Older models of the Playstation 3, made between November 2006 and August 2007, contain hardware for backwards compatibility. Specific model numbers "CECHA01," "CECHB01" and "CECHE01," found on the back-left rear of the unit beneath the bar code, denote the older models with the needed hardware to play Playstation 2 titles.
While not all PS2 games work perfectly in a PS3 with backwards compatibility, the Sony Playstation Compatibility Site lists "Grand Theft Auto: San Andreas" as a working title. An easy way to see if a PS3 is a reverse-compatible models is to check how many USB ports are on the unit. PS3s with backwards compatibility have four USB ports, whereas all other units have two. After November 2007, Sony removed the hardware necessary to emulate a PS2, although newer units can still play original Playstation software.