Title: Ans: (b)
1- Given the importance of registers, what is the
rate of increase in the number of registers in a
chip over time? - Very fast They increase as fast as Moores law
- Very slow They only increase as the instruction
set changes
- Ans (b)
- Moores law projects the doubling of transistors
every couple of years and has nothing to do with
registers. - The number of registers will change only if
instruction set architecture is changed. Because
machine code has only 5 bits to represent each
register, so it would require a substantial
change (a new ISA)
2- 2. Define the R-format instruction
- What are the various fields?
- What is the basic lay-out?
- What does each field represent?
- Are all of the bits used / needed for each field?
- Given an example of an R-format instruction in
MIPS assembler and the corresponding machine code
- Fields
- Op-code operation code
- Rs, Rt source registers
- Rd destination register
- SA shift amount
- Funct-code function specifier
Example add r1, r2, r0 000000 00010
00000 00001 00000 100000
3- 3. Define the I-format instruction
- What are the various fields?
- What is the basic lay-out?
- What does each field represent?
- Why this instruction format needed as opposed to
the R-format? - Give an example of an I-format instruction in
MIPS assembler and the corresponding machine code
- Fields
- Op-code operation code
- Rs source register
- Rt destination register
- Immediate 2s complement constant
Example addi r1, r2, 1 001000 00010
00001 0000000000000001
44. What is the range of addresses for conditional
branches in the MIPS ISA?
5- 5. Answer the following questions as true or
false - The beq instruction always modifies the program
counter register - The add instruction does not modify the PC
- The jal instruction always modifies the PC
- The instruction beq r1,r2,1 will advance the PC
by one byte if r1r2 - The instruction beq r1,r2,1 will advance the PC
by one word if r1r2
- Ans
- T. PC PC4 even if r1 ltgt r2
- F. PC PC4
- T. Unconditional branch
- F. PC PC4 4 x 1
- F. PC PC4 4 x 1
66. Find the shortest sequence of core MIPS
instruction to determine the absolute value of a
twos complement integer. Please the result into
r3.
- There are several possible answers to this
question. - However, in general, all involve the following
two steps - Convert the number to a positive value if it is
negative, which can be done by multiplication,
xor, nor, etc - Move the value to r3
77. Write out the truth table, the logic equation
and draw the gates for the Sum bit of a 1-bit
adder
Sum bit is 1 if an odd number of the three inputs
1 ?XOR the three inputs