move Rdest, Rsource
Move the contents of Rsource to Rdest.
The multiply and divide unit produces its result in two additional registers, HI and LO. These instructions move values to and from these registers. The multiply, divide, and remainder instructions described above are pseudo instructions that make it appear as if this unit operates on the general registers and detect error conditions such as divide by zero or overflow.
mfhi RdestFrom HI
mflo RdestFrom LO
Move the contents of the HI (LO) register to register Rdest.
mthi RdestTo HI
mtlo RdestTo LO
Move the contents register Rdest to the HI (LO) register.
Coprocessors have their own register sets. These instructions move values between these registers and the CPU's registers.
mfcz Rdest, CopsourceFrom Coprocessor z
Move the contents of coprocessor z's register Copsource to CPU
register Rdest.
mfc1.d Rdest, FRsrc1Double From Coprocessor 1 
Move the contents of floating point registers FRsrc1 and
FRsrc1 + 1 to CPU registers Rdest and Rdest + 1.
mtcz Rsource, CopdestTo Coprocessor z
Move the contents of CPU register Rsource to coprocessor z's
register Copdest.