Computer Architecture 120-CT
Questions
Explain an assembler - Answer-Assembler is a program that translates assembly language into machine
code.
What are buses - Answer-Buses is the collection of wires that transfer data from one part of the machine
to another. There are normally three types of buses in any computer system: address bus, data bus and
control bus.
What is superscalar pipeline - Answer-Superscalar pipeline introduces the ability to execute instructions
independently and concurrently in different pipelines which enables more instructions executed in every
clock period. A superscalar processor contains multiple copies of the datapath hardware to execute
multiple instructions simultaneously.
What is an Instruction Set - Answer-The collection of different operations that a processor can execute
What is machine code - Answer-Each instruction of a program is encoded into a binary format that a
processor has to decode to realize the operation and then execute it.
Distinguish among the following types of assembly language statements:
a. Instructions
b. Directives - Answer-Instructions are the operations which are executed by the CPU. Directives do not
represent machine instructions; hence they are not executed at run-time. They direct the assembler to
do something while translating the program to machine language, such as allocate space for a variable
and give it an initial value, which it will have when the program begins executing. All assembler
directives have names that begin with a period ".". The rest of the name is letters, usually in lower case.
, What is meant by general-purpose registers and describe how they have an impact on the classification
of the CPU architecture? - Answer-They store either a data or a memory location address (hence called
as general-purpose register). They are a multipurpose register that can be used by a programmer. CPU
architecture can be classified according how many general-purpose registers they have:
· An accumulator-based CPU has one general purpose register (the accumulator). The accumulator is a
register which is used as a source and/or a destination of an arithmetic/logic operation
· A register-based CPU has many general-purpose registers. Its main advantage is that it is easier for the
CPU to do more independent instruction in parallel. Recent CPU designs accommodate this architecture
by having dozens of general-purpose registers
Draw the instruction cycle. Identify the four registers which participate in the instruction cycle and the
data they hold during it. - Answer-Four registers are essential for an instruction execution. They are used
for the movement of data between the processor and memory.
Program Counter Register (PC)
Contains the address of an instruction to be fetched next time
Instruction Register (IR)
Contains the instruction most recently fetched
Memory Address Register (MAR)
Contains the address of a location in memory that requires to be fetched
Memory Data Register (MDR)
Contains a word of data to be written to memory or the word most recently read
What is meant by ISA and explain its design issues? - Answer-Instruction Set Architecture (ISA) is the
interface which is provided by the architect to the external world. Issues when designing ISA:
· Types of Instructions: The instructions that are supported with their operation code opcode (The binary
representation of instruction mnemonics)
· Number of Operands: The width (number of bits) of data, data address, how many operands are
available in instructions, does the instruction set has a fixed or variable number of operands.
· Addressing Modes: The available methods which are used to specify the location of operands.
Questions
Explain an assembler - Answer-Assembler is a program that translates assembly language into machine
code.
What are buses - Answer-Buses is the collection of wires that transfer data from one part of the machine
to another. There are normally three types of buses in any computer system: address bus, data bus and
control bus.
What is superscalar pipeline - Answer-Superscalar pipeline introduces the ability to execute instructions
independently and concurrently in different pipelines which enables more instructions executed in every
clock period. A superscalar processor contains multiple copies of the datapath hardware to execute
multiple instructions simultaneously.
What is an Instruction Set - Answer-The collection of different operations that a processor can execute
What is machine code - Answer-Each instruction of a program is encoded into a binary format that a
processor has to decode to realize the operation and then execute it.
Distinguish among the following types of assembly language statements:
a. Instructions
b. Directives - Answer-Instructions are the operations which are executed by the CPU. Directives do not
represent machine instructions; hence they are not executed at run-time. They direct the assembler to
do something while translating the program to machine language, such as allocate space for a variable
and give it an initial value, which it will have when the program begins executing. All assembler
directives have names that begin with a period ".". The rest of the name is letters, usually in lower case.
, What is meant by general-purpose registers and describe how they have an impact on the classification
of the CPU architecture? - Answer-They store either a data or a memory location address (hence called
as general-purpose register). They are a multipurpose register that can be used by a programmer. CPU
architecture can be classified according how many general-purpose registers they have:
· An accumulator-based CPU has one general purpose register (the accumulator). The accumulator is a
register which is used as a source and/or a destination of an arithmetic/logic operation
· A register-based CPU has many general-purpose registers. Its main advantage is that it is easier for the
CPU to do more independent instruction in parallel. Recent CPU designs accommodate this architecture
by having dozens of general-purpose registers
Draw the instruction cycle. Identify the four registers which participate in the instruction cycle and the
data they hold during it. - Answer-Four registers are essential for an instruction execution. They are used
for the movement of data between the processor and memory.
Program Counter Register (PC)
Contains the address of an instruction to be fetched next time
Instruction Register (IR)
Contains the instruction most recently fetched
Memory Address Register (MAR)
Contains the address of a location in memory that requires to be fetched
Memory Data Register (MDR)
Contains a word of data to be written to memory or the word most recently read
What is meant by ISA and explain its design issues? - Answer-Instruction Set Architecture (ISA) is the
interface which is provided by the architect to the external world. Issues when designing ISA:
· Types of Instructions: The instructions that are supported with their operation code opcode (The binary
representation of instruction mnemonics)
· Number of Operands: The width (number of bits) of data, data address, how many operands are
available in instructions, does the instruction set has a fixed or variable number of operands.
· Addressing Modes: The available methods which are used to specify the location of operands.
