Computer Architecture
Assignment#1
Due Date: ________
Max Marks: 100
Plagiarism policy: Do not try to copy. Students involved will be given zero straight away.
Read your book carefully to answer the following questions.
Question 1: Consider the instruction set given below for a 16-bit microprocessor having 3000 bytes of
memory. Microprocessor also supports memory direct, and indirect addressing mode.
Mnemonic
Operation
OPCODE
LDA
Load
addressed
memory
contents into accumulator
Store value of Accumulator so
specified memory address.
ADD
addressed
memory
contents to accumulator
XOR
addressed
memory
operand with Accumulator
Complement
value
of
Accumulator
Transfer value of accumulator
into output register
Increment
the
value
of
Accumulator
ADD
addressed
memory
contents to accumulator
000
STA
ADD
XOR
COM
OUT
INC
ADD
For the specified microprocessor, what will be the instruction format?
001
010
011
100
101
110
111
(5)
Question 2: The initial contents of AC and E for all the instructions in basic computer are hexadecimal
A937 and 1 respectively. The initial value of PC is hexadecimal 021. The size of memory is 4096×16.
Determine the value of AC, E, PC, AR and IR in hexadecimal when the following register reference
instructions are executed:
(50)
a)
b)
c)
d)
CLA (7800)
CLE (7400)
CMA (7200)
CME (7100)
e) CIR (7080)
f) CIL (7040)
g) INC (7020)
h) SPA (7010)
i) SNA (7008)
j) SZA (7004)
k) SZE (7002)
l) HLT (7001)
Question 3: All numbers in this problem are hexadecimals. The instruction at address 021 in the basic
computer has I=0 and an address part 083. The memory word at 083 contains operand B8F2 and the
contents of AC is A937. You only need to write the final values after the complete execution of
instruction.
Show the contents of PC, AR, DR, AC and IR in hexadecimal after the execution of the
following memory reference instructions. (35)
a)
b)
c)
d)
e)
f)
g)
AND (0083)
ADD (1083)
LDA (2083)
STA (3083)
BUN (4083)
BSA (5083)
ISZ (6083)
Question 4: A digital Computer has a memory unit with capacity of 16384 words, 40 bits per work. The
instruction code format consists of 6 bits for operation part and 14 bits for address part (no indirect
addressing mode bit). Two instructions are packed in one memory word, and a 40-bit instruction register
is available in control unit. Formulate the procedure of instruction and fetching and execution cycle for
this computer (10).
Question 5: (Bonus Question-50. Search from internet or any book. Not your course outline part)
Compare the performances of two computers M1 and M2. The following measurements has been made
on these computers
Program
Time on M1
Time on M2
1
2.0 seconds
1.5 seconds
2
5.0 seconds
10.0 seconds
Program
1
Instructions executed on M1
5 × 109
Instructions executed on M2
6 × 109
a) Which computer is faster for each program, and how many times as fast is it?
b) Find the instruction execution rate (instructions per second) for each computer when running
program1
c) The clock rates for M1 and M2 are 3 GHz and 5 GHz respectively. Find the CPI for program 1 on both
machines.
d) Suppose that program 1 must be executed 1600 times each hour. Any remaining time should use to
run program 2. Which computer is faster for this workload?