ECM 1413 Computer Architecture

Question 1

Main components of a computer

Answer 1

1 the central processing unit
2 the memory
3 the input/output devices

Question 2

Positional Numeral systems

Answer 2

The contribution of a digit to the value of a number is the value of the digit multiplied by a factor determined by the position of the digit

Question 3

Two common ISAs used by cpus

Answer 3

ARM
x86

Question 4

Instruction set architecture (ISA)

Answer 4

Part of the abstract model of a computer that defines how the CPU is controlled by the software. The ISA acts as an interface between the hardware and the software, specifying both what the processor is capable of doing as well as how it gets done.

Question 5

In essence, what is a register?

Answer 5

Registers are small fast memory locations in the cpu
When executing a given process, that process’s registers are loaded into the cpu

Examples of registers for purposes (AX, BX are 16 bit registers, extended to RAX and RBX in x64 and x86 architectures)

Question 6

Special-purpose registers

Answer 6

Base Pointer (BP)
Stack Pointer (SP)
Link Register (LR)
Program Counter (PC)
Current program status register/flags (CPSR)

Question 7

Stack pointer

Answer 7

points to the top of the stack

Question 8

Base pointer

Answer 8

points to the start (base) of the current frame

Question 9

Link Register

Answer 9

stores the address where to return to when the current function call has completed

Question 10

Program Counter

Answer 10

stores the address of the next instruction to be executed

Question 11

The Arithmetic Logic Unit (ALU)

Answer 11

performs simple operations between two input registers (operands) and puts the result in an output register

The current program status register contains status and control bits indicating, for example, the output of the ALU and the mode of the CPU

Question 12

Current program status (Flag) Register

Answer 12

contains status and mode bits

Question 13

Assembly language summarised

Answer 13

Simple instructions
Difficult programming language
An assembly level instruction often references one or multiple registers

Question 14

Hierarchy of memory

Answer 14

(Top = fastest, bottom = slowest)

Registers: Flip-flop 32/64 bit
Cache: Static RAM (Latch circuit) L1, L2, L3
Main memory: Dynamic RAM (capacitor & transistor)
Disks: HDDs and SSDs

Question 15

Distinguishments between code and data

Answer 15

Code and data are kept separate by memory
Code is executed
Data is read and written

Question 16

The minimum addressable unit of memory

Answer 16

typically 1 byte

Question 17

A memory with 2^n addressable units will need:

Answer 17

n-bit addresses