COMPUTER ARCHITECTURE(BCS504)
Unit I
2 – MARKS
1. What is computer Architecture?
It is concerned with structure and behavior of computer as seen by the user. It
includes the information formats, the instruction set, and techniques for addressing
memory of a computer system is concerned with the specifications of the various
functional modules, such as processors and memories and structuring them together
into a computer system.
2. What are the elements of computer?
Input unit
Memory unit
Arithmetic and logic unit
Control unit
Output unit
3. List the instructions supported by IAS computer.
Data transfer
Unconditional branch
Conditional branch
Arithmetic
Address modify
4. What is the function of Control Unit?
The control unit acts as the nerve center that coordinates all the computer
operations. It issues timing signals that governs the data transfer.
5. Define addressing modes?
The different ways in which the location of an operand is specified in
instructions are referred to as addressing modes.
6. Define bus?
A group of lines that serves as a connecting path for several devices is called a
bus.
7. Define register?
A register is a group of flip- flops. A flip – flop can store 1 bit information. So an
n bit register has a group of n flip- flops and is capable of storing any binary
information/ number containing n – bits.
8. What are the steps in executing a program?
1. Fetch
2. Decode
3. Execute
4. Store
9. Briefly explain the floating point representation with an example?
The floating point representation has three fields : sign , significant digits and
exponent.
For example consider 1.11101100110*25
Sign = 0
Mantissa = 11101100110
Exponent = 5
10. What are the elements of instruction?
Each instruction of the CPU contains specific information fields, which are
required to execute it. These information fields of instructions are called elements of
instruction. These are
Operation code
Source/destination operand
Source operand address
Destination operand address
Next instruction address.
UNIT –II
2 – Marks
1.What is the advantages in 1’s complement subtraction?
The 1’s complement subtraction can be accomplished with an binary adder.
Therefore, this method is useful in arithmetic logic circuits.
The 1’s complement of a number is easily obtained by inverting each bit in
the number.
2. Give an example for the worst case of Booth algorithm
The worst case is shown as below
010101010
+1 -1 +1 -1 +1 -1 +1 -1 +1
In the worst case each bit of the multiplier selects the summands. This results in more number of
summands.
3. Write the steps for subtracting larger number from smaller number in 1’s
complement?
Determine the 1’s complement of smaller number.
Add the 1’s complement to the larger number.
Answer is in 1’s complement form. To get the answer in true form take the
1’s complement and assign negative sign to the answer.
4. What are the problems in floating point arithmetic?
Mantissa overflow
Mantissa underflow
Exponent overflow
Exponent underflow
5. What is meant by carry propagation delay.
6. What is temporal expansion?
In this, one copy of the m-bit ALU in the manner of serial adder performs an
operation of km- bits words in K consecutive steps. This processing is commonly
known as multicycle or multi- precision processing. In each step the m-bit ALU
processes a separate mbit slice of each operand.
7. What is coprocessor?
Coprocessor is a separate instruction set processor. It has its own instruction set
supporting the special exponential and trignometric functions. The instructions and
registers of coprocessor are just extension of the CPU’s instruction set and registers.
8. What is pipelining?
Pipelining is a technique where multiple instruction are overlapped in execution
for increasing processor throughput.
9. What is throughput?
The maximum number of operations completed per second can be gives as 1/T.
10. Solve the following using 2’s complement arithmetic.
a) Subtract 101011 from 111001 b) Subtract 111001 from 101011
111001 + 010101 (2’s complement of 101011)= 001110
101011 + 000111 (2’s complement of 111001)= 110010(2’s complement form)
= -001110(true form)
UNIT –I
16 Marks
1. Explain the various addressing modes?
• Immediate
• Direct
• Indirect
• Register
• Register Indirect
• Displacement (Indexed)
• Stack
Immediate Addressing
• Operand is part of instruction
• Operand = address field
• e.g. ADD 5
— Add 5 to contents of accumulator
— 5 is operand
• No memory reference to fetch data
• Fast
• Limited range
Direct Addressing
• Address field contains address of operand
• Effective address (EA) = address field (A)
• e.g. ADD A
— Add contents of cell A to accumulator
— Look in memory at address A for operand
• Single memory reference to access data
• No additional calculations to work out effective address
• Limited address space
Indirect Addressing(1)
• Memory cell pointed to by address field contains the address of (pointer to) the
operand
• EA = (A)
— Look in A, find address (A) and look there for operand
• e.g. ADD (A)
— Add contents of cell pointed to by contents of A to accumulator
Indirect Addressing (2)
• Large address space
• 2n where n = word length
• May be nested, multilevel, cascaded
— e.g. EA = (((A)))
– Draw the diagram yourself
• Multiple memory accesses to find operand
• Hence slower
Register Addressing
• Operand is held in register named in address filed
• EA = R
• Limited number of registers
• Very small address field needed
— Shorter instructions
— Faster instruction fetch
Register Indirect Addressing
• C.f. indirect addressing
• EA = (R)
• Operand is in memory cell pointed to by contents of register R
• Large address space (2n)
• One fewer memory access than indirect addressing
Displacement Addressing
• EA = A + (R)
• Address field hold two values
— A = base value
— R = register that holds displacement
— or vice versa
Relative Addressing
• A version of displacement addressing
• R = Program counter, PC
• EA = A + (PC)
• i.e. get operand from A cells from current location pointed to by PC
• c.f locality of reference & cache usage
Indexed Addressing
• A = base
• R = displacement
• EA = A + R
• Good for accessing arrays
— EA = A + R
— R++
2. Write briefly about the Von-Neumann Architecture.
3. Explain about register level in detail?
4. Discuss about processor level in detail
5. Discuss in detail about the fixed point numbers?
UNIT – II
1. Explain the Robertson algorithm for 2’s Complement Multiplication of 5x4.
2. Write short notes on carry look ahead adder in detail?
3. Explain the Booth’s algorithm for signed multiplication of 5x4.
4. Describe the pipeline processing and its design in detail?
Pipelining
– Comes from the idea of a water pipe: continue sending water without
waiting the water in the pipe to be out
– leads to a reduction in the critical path
– Either increases the clock speed (or sampling speed) or reduces the power
consumption at same speed in a DSP system
• Parallel Processing
– Multiple outputs are computed in parallel in a clock period
– The effective sampling speed is increased by the level of parallelism
– Can also be used to reduce the power consumption
5. Explain about the Non-Restoring division operation of 10x3 with flowchart.
