well actually P89V51RD2 is not PIC controller it's a 8051 from Philips.
RD2 means 12 clocks per machine cycle as P89v51RD2 provides 2 possibilities (features) to use it: 1) is 6 clock cycle/machine cycle
& 2) is 12 clock cycle / machine cycle.
12 clock cycle / machine cycle is the default choice.
& this is the reason why we need to include "x" in the header file of this controller during programming.
Ex. #include<p89v51rx2.h> So this x represents that feature which I mentioned above.