4.7 - Fundamentals of computer organisation and architecture Flashcards
What is main memory?
A place where the computer stores program instructions and frequently used data, consisting of the RAM (random access memory) and ROM (read only memory).
What is the benefit of main memory?
It is much faster than secondary storage so storing frequently used data helps the processor execute instructions quickly.
What is a bus?
A series of parallel wires that connects internal components of a computer, allowing signals to pass between them.
What is the address bus?
A bus used to transport memory addresses, specifying where data is to be sent or retrieved from.
What is the data bus?
A bus used to send data and instructions to and from different components of a computer.
What is the control bus?
A bus used to carry control signals that regulate the operation of the computer system. It also carries the clock signal.
What are I/O controllers?
Pieces of hardware that control the communication of data between the processor and external hardware devices.
How do Harvard and Von Neumann architecture differ?
Harvard : Two separate memory locations (and sets of buses), one for instructions, the other for data.
Von Neumann : Both instructions and data stored in same memory and share the same buses
Why is Harvard architecture considered better than Von Neumann architecture?
It avoids the bottleneck of a single set of buses and avoids the possibility of data being executed as instructions. It also allows each part of memory to have different characteristics, such as making instruction memory read only.
What is the stored program concept?
A computer that uses the stored program concept serially fetches and executes machine code instructions stored in main memory by a processor that performs arithmetic and logical operations.
Why is the stored program concept important?
It forms the foundation of modern computers. Early computers were designed to execute one specific program, but the stored program concept allows one set of instructions to be switched out for another, so numerous different applications can be run.
What is a processor’s instruction set?
The group of instructions that it can carry out. Each type of processor has its own instruction set, so instructions for one may not be compatible with others.
What are the two primary parts of an instruction?
Opcode, which specifies the type of operation as well as the addressing mode.
One or more operands, which are the pieces of data on which the operation is performed.
What is immediate addressing?
The value specified in the operand is to be treated as the actual value to use.
What is direct addressing?
The value specified in the operand signifies a memory address to access.
What is an interrupt?
A signal sent to the processor by another part of the computer requesting the attention of the processor.
How are interrupts handled?
It is first detected as a change in the content of the status register between the execute and fetch stages of the FDE cycle.
Then, the processor stops executing the current program and places the content of its registers onto the system stack, known as ‘saving the volatile environment’.
Now that it has saved its progress, loads appropriate interrupt service routine (series of instructions for handling a specific interrupt).
Once ISR finished, processor restores volatile environment from system stack and resumes execution of any programs running before the interrupt.
How does the number of cores affect processor performance?
Each core can perform its own FDE cycle independently of others, so different applications can be allocated different cores. This means that multiple tasks can be processed at the same time, increasing efficiency.
How does cache memory affect processor performance?
Cache memory is a small portion of incredibly fast memory, with read and write speeds far higher than HDDs and even SSDs. It stores frequently used information and reduces time wasted in fetching the same information from main memory time and time again. The more cache memory, the more information it can store and the more time it can save in fetching information from main memory.
How does clock speed affect processor performance?
The higher the frequency of pulses, the more cycles of the FDE cycle can be completed per unit time. However, errors can occur when clock speed is increased too far, and the processor can overheat.
How does word length affect processor performance?
A word is a group of bits treated as a single unit by the processor, and can represent instructions or data. Word length is the number of bits assigned to it, so higher word length allow more bits to be transferred and manipulated as a single unit.
How does address bus width affect processor performance?
Increasing width increases range of addresses it can specify, hence increasing computer’s amount of addressable memory.
How does data bus width affect processor performance?
Increasing width increases volume of data that can be transferred over the bus at any one time. More data can be fetched per cycle, reducing number of cycles required to fetch large volumes of data.
How does a barcode reader work?
Consists of a laser light source, a lens, photodiodes and a mirror.
Mirror directs laser onto barcode. Light reflected by barcode passes through lens and is incident on photodiode which turns light into electrical charge. Charge measured and processed to form digital signal representing content of barcode.
Barcodes have error detection and prevention built in such as parity bits and check digits, which indicate if barcode has been read correctly.
