Mid Term Exam Flashcards
What is meant by the term “Semiconductor” ? Give an example of a semiconductor and what is the function of a dopant ?
A semiconductor is an element that is a poor conductor of electricity, but which can be converted to being a good conductor (like a metal) through doping.
E.g. Silicon
A dopant increases the conductivity of a semiconductor by introducing mobile carriers. I.e., electrons or holes.
What is meant by the term “von Neumann computer architecture” ?
Three components constitute the Von Neumann Architecture
1. Processor
2. I/O
3. Memory
Memory stores data and the program in digital format
What is the approximate size of a transistor ?
Approximate size of a transistor of order of 10^-9
What is the approximate clock frequency of modern laptop ?
3 x 10^9 Hz
What was the standard General User Interface (GUI) for a computer in the era 1960-1970 ?
Punch cards
Keyboard
Paper printouts
Dumb terminals (Screens)
Give three physical differences between a Main-Frame computer of the 1960-1980s and a Microprocessor.
Main Frame: Consists of several transistor boards
Huge electricity consumption kW
Physical size equivalent to several filing cabinets
Requires a controlled environment
Processing rate. 10’s millions instr/sec
Microproccessor:
1 silicon chip
Size of a match box
Energy consumption 1-10 W
Up to 1 million instructions/sec
Operates in a normal office environment
What is Moore’s Law and what has been its impact on the evolution of the Microprocessor ?
Moores Law: Every 18 months transistor density doubles
This has lead to an exponential growth in the complexity of chips
From 1980 to 2016: 24 18 month periods
1980 = 1000 transistors/chip
10^3 x 2^24 = 16 billion
What is meant by the term “von Neumann Bottleneck” ?
The no. of instructions executed/sec is determined by the memory bandwidth. (E.g. how many bytes per second can be transferred from memory to the CPU) how fast you can read and write to memory
What is the function of the Program Counter ?
The program counter contains the address of the next instruction to be executed. It is incremented at the decode phase by the length of the current instruction.
What is the function of the Op-code in an instruction ? What details does it give to the CPU when it is decoded?
The opcode informs the processor on:
The operation to be executed.
The length of the instruction
The type and number of operands involved in the instruction execution.
What is the minimum unit of information transferrable from memory ?
A byte
How is a bit of information/logic values electronically represented?
Voltage 0v, 5v
What are the 3 phases in an instruction cycle ?
Fetch, Decode, Execute
What is DeMorgan’s Law?
¬(A . B) = ¬A + ¬B
¬(A + B) = ¬A . ¬B
What is the critical path delay of a circuit?
The longest time it takes for a signal to travel from input to output
The most basic Logical device in a computer system is?
A gate. (Transistor is smaller but not a logical device)
What is a stack and a stack pointer? How are they used in subroutines?
Stack: LIFO area of memory used for subroutine linkage
Stack Pointer: Register that holds address (pointer) of top of stack
What is the address range of a computer with a 24-bit address bus and a 32-bit data bus? Solve generally first.
2^(bits in address bit) - 1.
