The latest version of RVDK (RealView Development Kit) supplied by Keil is μvision4. The evaluation version of this is freely downloadable by looking up ‘Keil μ Vision 4’ or from the link
The evaluation version can be used for simulation, and the only limitation it has is that a memory limitation of 2K for program code for 8051.
The ‘RealView Development Kit (RVDK) of Keil’ is a tool chain consisting of assemblers, compilers, debuggers, simulators, etc. for many chips of many families – it caters to the 8051 family, ARM and many more families of chips. It can be used for C programming of embedded devices as well as assembly language programs.