The width of the data bus on the 8051 microcontrollers is 8 bits, meaning it can handle up to 256 different values in each group of data. It has an 8-bit data address bus which means it can access up to 64K separate memory addresses for accessing program instructions and data. The width of the address bus also allows for a few ports to be located in the same memory space that, allows for more than 256 I/O pins.   However, not all models of 8051s are capable of supporting this configuration and will require extra circuitry instead. Its distributed architecture ensures high performance with strict timing requirements, making it ideal for a wide range of embedded applications.