8051 with keil C51 compiler

will it support for any 8051 core based uC e.g. P89C668/AT89c51/P89C51RD2

8051 with keil C51 compiler

The core components of the 8051 will be transferable across all the 8051 variants – as per the ARM7 port which is used on many different ARM7 devices.  However, the setup on non standard 8051 peripherals, clock frequencies, etc. will be different for different devices.  There is a section on the 8051 port WEB page about using different devices. Also, many 8051 devices are too slow of have too little memory to do anything useful with an RTOS. There is however NOT currently Keil support for the 8051, only SDCC. Regards.