Q Assume that we would like to expand the MIPS register file

Q: Assume that we would like to expand the MIPS register file to 128 registers and expand the instruction set to contain four times as many instructions

1. How this would affect the size of each of the bit fields in the R-type instructions

2. How this would affect the size of each of the bit fields in the I-type instructions

3. How could each of the two proposed changes decrease the size of an MIPS assembly program? On the other hand, how could the proposed change increase the size of an MIPS assembly program?

Solution

a)

Log 2 (128) = 7

opcode = 6

rs = 7

rt = 7

rd = 7

shamt = 5

funct = 6

b)

Log 2 (128) = 7

opcode = 6

rs = 7

rt =

immediate = 16

c.)

If the instruction encoding is longer that means program also will be longer with same operations. This means that the format may be larger because the increases are not aligned. If there are more registers then that means that they can hold more information/data without going out to memory leading to fewer calls of load/store so the code will decrease.