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Computer Organization (0306-550) - Winter 2009
Homework Assignment #3 - Due January 14
1. You are to add support for the jr (jump register) MIPS instruction to the MIPS
single-cycle datapath of 4rd Edition figure 4.17 page 322 (3rd Edition figure 5.17
page 307).
a) Add necessary datapath components, connections, and control signals
to support this instruction. Justify the need for the modifications.
b) Specify control line values for this instruction by adding a new row for
jr to the control table in 4rd Edition Figure 4.18 page 323 (3rd Edition
Figure 5.18 page 308).
2. You are to add support for a new instruction l_inc (load increment) to the
MIPS single-cycle datapath of 4rd Edition figure 4.17 page 322 (3rd Edition
figure 5.17 page 307). The l_inc instruction is a variant of lw (load word)
which increments the base address register after loading from memory. This
instruction (l_inc) corresponds to the following two instructions:
lw $rt, L($rs)
addi $rs, $rs, 4
Where L is just the usual offset. You may assume that register specifiers
$rs,$rt do not refer to the same register.
a) Add necessary datapath components, connections, and control signals
to support this instruction. Justify the need for the modifications.
b) Specify control line values for this instruction by adding a new row for
l_inc to the control table in 4rd Edition Figure 4.18 page 323 (3rd
Edition Figure 5.18 page 308).
c) Explain why it is not possible to modify the single-cycle datapath to
support the l_inc instruction without modifying the register file.
