1.1- Systems Architecture Flashcards
Von Neumann
Computing pioneer from Hungary who gave his name to a computer architecture that uses stored programs. Instructions are fetched, decoded and executed one at a time.
Fetch
The phase of the instruction cycle that retrieves an instruction from main memory
Decode
This phase of the instruction cycle determines what task the CPU must perform
Execute
The phase of the instruction cycle wherebthe task is carried out, which could be an arithmetic shift, logic or memory operation
Fetch-Execute Cycle
Also known as the instruction cycle, the complete process of retrieving an instruction from store, decoding it and carrying it out
Instruction
A single operation, one of these is executed each time the CPU performs the fetch-execute cycle
Main memory
Also known as RAM or Primary Storage, this is where data and instructions are stored in the Von Neumann architecture
Process
Computers take input, and produce output. This is what happens in between, which needs a CPU
Stored program
Von Neumann invented this concept, it means keeping the instructions in memory instead of inputting them each time through switches or paper tape
Central Processing Unit
This component repeatedly fetches, decodes and executes instructions. Often abbreviated to CPU
Architecture
The design of a computer, including the way its components are organised and the rules that male them work together. Von Neumann invented a type of this
Memory Address Register (MAR)
• Location address in memory of the next piece of data or instruction to be fetched or stored
Memory Data Register
A register that stores the data being sent to or retrieved from memory. This could be data to be processed, or an instruction being fetched.
Accumulator
A register in the ALU that holds data temporarily. It stores the results of calculations and logical operations.
Program Counter
• Continuously provides the CPU with the memory address of the next instruction in the cycle to be fetched.
Registers
The collection of tiny areas of extremely fast memory located in the CPU, each with a specific purpose, where data or control information is stored temporarily. Examples are the MAR, MDR, PC and Accumulator
Cache
A small amount of fast memory in the CPU. It stores the data and instructions most likely to be needed again and it is faster to access than RAM
Arithmetic Logic Unit (ALU)
• Where calculations are carried out
• These include: mathematical tasks, logic tests, data comparisons
Bus
Any of three communication pathways between the CPU and RAM in the Von Neumann architecture. There is one for addresses, one for data and one for control signals
Control Unit
Component of the CPU which controls the flow of data around the CPU, communication between the CPU and input and output devices, and decodes and executes instructions
Clock
Component of the CPU which synchronises all activity in the computer. It regulates the speed at which instructions are completed
RAM
• Temporary area that a computer uses to store data in current use
• Much quicker to access than the computer’s hard drive
• Quickly recalls information
Small
The size of the cache memory, compared to RAM
Fast
The speed of the cache memory, compared to RAM
Core
A single processing unit in a CPU. It contains a full set of components: CU, ALU and Registers and can execute a single instruction every clock cycle
Dual Core
A CPU with two processing units. It can execute up to two instructions every fetch-execute cycle
Quad Core
A CPU with four processing units. It can execute up to four instructions every time the clock ticks
Clock Speed
The speed of operations in a CPU, it’s the number of fetch-execute cycles performed in one second. Usually measured in GigaHertz (GHz). Speeding this up will improve performance.
Hertz
A unit of frequency, the number of times per second something happens.
Cache
If this is larger it will speed up the computer because the CPU will do fewer fetches from RAM. It is small, fast memory inside the CPU
Multitasking
An operating system feature that allows the computer to run many programs at the same time, which can take advantage of multicore CPUs
Parallel processing
Executing multiple instructions of the same program at the same time, which can make good use of multicore CPUs
GigaHertz
Clock speeds are usually measured with this large unit, it means a billion cycles per second
Multicore
General term for any CPU that contains more than one core. Each core is an independent processor with ALU, CU and Registers and can execute one instruction per clock cycle.
2 billion
Number of instructions per second executed by a single core CPU with a clock speed of 2GHz
4 billion
Number of instructions per second executed by a quad core CPU with a clock speed of 1GHz (assuming the programs are all suitable for multitasking or parallel processing and so make full use of all cores)
3 billion
Number of instructions per second executed by a dual core CPU running at 1.5GHz (assuming the programs are all suitable for multitasking or parallel processing and so make full use of all cores)
Performance
The speed a computer runs your programs, it is affected most by clock speed, number of cores and size of cache memory.
Embedded system
A computer system dedicated to a single function within a larger electrical or mechanical system
Dedicated
Having a single purpose or function, not general purpose. Embedded systems are this
General purpose
A computer system that can have many uses, it can run application software and do more than one thing
Small
The relative size of embedded systems, compared to general purpose computers
Cheap
The cost of an embedded system compared to a general purpose computer
Control system
An embedded system in traffic lights or a dishwasher manages the hardware, turning things on and off. We often use this two word phrase to describe such a computer
Desktop computer
An example of a general purpose computer. It sits on the desk and runs a multi-tasking operating system such as Windows or macOS
Efficient
An example of a general purpose computer. It sits on the desk and runs a multi-tasking operating system such as Windows or macOS
Multitasking
Running more than one program at once. General purpose computers can do this, embedded systems cannot
Traffic lights
Signals that instruct drivers to stop and go, they are controlled by an embedded system whose one function is to control the lights
Dishwasher
Home appliance to wash plates, the computer in this device has only one job, to control the valves and heaters in the machine
Power
Embedded systems consume a lot less of this, meaning they can run for a long time on batteries or solar energy
Memory
Memory
General purpose computers need a lot of this, because they are designed to run many different programs. Embedded systems don’t need to store a lot of instructions or data so this can be small
