What is difference between 8051 and 8951?

umm 1? lol No, seriously, as explained on www.8052.com, the 8052 has twice the RAM of the 8051 (that is 256 Bytes), an additional 16-bit Timer (Timer 2) and more Special Function Registers (SFR) as required for the additional features. The most essential difference is that Timer2 can be used as a Baud rate generator for serial communication.