Unit 1: System Architecture Flashcards
What is the CPU and what is its role?
Internal hardware component of the computer that is responsible for executing instructions of programs. It is made up of many important components, each with its own role.
What is the function of the CU?
- Manages the fetching, decoding and executing of program instructions. (Fetch, Decode Execute)
- Controls the flow of data inside the CPU (to registers, ALU, cache) and outside the CPU (to main memory and input/output devices)
What is the function of the ALU?
- Performs logic operations (AND, OR, NOT) and binary shifts.
- Performs arithmetic calculations including adding, subtracting, comparing sizes of numbers, multiplication and division.
- Contains the accumulator register.
What is the function of the Cache?
- Very fast memory in the CPU (Slower than registers, faster than RAM)
- Stores regularly used data so it can be accessed quickly by the CPU when it’s needed. (When the CPU request data, it checks the cache first before fetching it from the RAM)
- Has a very low capacity and is expensive compared to RAM and secondary storage.
- 3 levels of Cache memory - L1 is quickest but has lowest capacity, L3 is slowest but holds the most.
What is the Von Neumann Architecture?
A system where the CPU runs programs stored in memory. Program consists of instructions and data which are stored in memory addresses.
What is the function of the MAR?
Holds the memory address of the current instruction, and then the data that it uses, so that these can be fetched from memory.
What is the function of the MDR?
Holds the actual instruction, and then the data that has been fetched from memory.
What is the function of the PC?
Holds the address of the next instruction to be executed.
What is the function of the Accumulator?
Stores intermediate results of calculations in ALU before it is transferred from memory.
To summarise, what are the steps involved in the fetch, decode, execute cycle?
All information in GoodNotes
CPU operates by repeating three operations:
FETCH - Causes the next instructions and any data involved to be fetched from main memory.
DECODE - Decodes the instruction.
EXECUTE - The instruction is executed.
All information in GoodNotes
What are embedded systems and how are they mainly used?
Embedded systems are computers built into other devices.
* E.G Dishwashers, Microwaves, TVs
* Often used as control systems - monitor and control machinery in order to achieve a desired result. E.G In a dishwasher, the embedded system could control the water pumps and water release mechanisms.
* Due to them being dedicated to a single task, they are often easier to design, cheaper to produce, and more efficient at doing their task than a general purpose computer.
What is the purpose of a computer and a computer system?
COMPUTER - Takes data, processes it, then outputs it.
COMPUTER SYSTEM - Hardware and software that work together to process data/complete tasks.
What does volatile and non-volatile memory mean?
VOLATILE - Temporary memory - requires power to retain its data.
NON-VOLATILE - Permanent memory - keeps its content even when it doesn’t have any power.
What is RAM?
Random Access Memory is used as main memory in a computer. It can be read and written to and is volatile.
* Main memory is where all data, files and programs are stored while they’re being used.
* When a computer boots up, the operating system is copied from secondary storage to RAM or when a software application is opened, the same process occurs. They stay in RAM until the application is closed
* Slower than CPU cache, faster than secondary storage.
What is virtual memory and when is it used?
- Computers have limited amounts of RAM and as applications are opened, RAM fills with data.
- When RAM is full, data that hasn’t been used recently is moved to a location on secondary storage (virtual memory)
- Virtual memory is needed if there are too many applications open at once or if a particularly memory intensive application is being used (or both)
- If the CPU needs to read data stored in virtual memory, it must move the data back to RAM which is slow as data transfer rates are much slower on secondary storage than RAM.