# Difference in the datapath of Load Upper Immediate to Load Word in a 32 bit MIPS processor

For the MIPS insturction Load Word I have got the following Datapath:

How does the datapath for the Instruction Load Upper Immediate looks like?

• Pretty much the same, but with no reading from Memory(data)? The value for LUI is encoded as the lower 16-bits of the 32-bit opcode. – Majenko Oct 15 '14 at 23:28

I had these pictures sitting around except for the red lines.

The two instructions differ in semantics:

$t is the destination register,$i is an immediate value.

LUI:

LW:

The images are all links to their full size versions.

In a real implementation the muxes to the ALU could likely produce 0 and 1 constants.

And along the bottom of those pipeline diagrams the \$t should actually be t, the pointer to the target or destination register.