1 - System Architecture Flashcards
(53 cards)
What are the main components of a computer?
CPU, Output and Input devices, Main Memory, Secondary Storage
What is the CPU?
Central Processing Unit- Processes instructions and acts as the “brains” of the computer.
What is the Von Newmann architecture?
Program instructions and data programs are using both stored in same memory. CPU accesses both instructions and data from same RAM.
What is the Control Unit?
Coordinates and controls activites taking place in CPU. Decodes and executes instructions, receives signals from system clock and directs timing and control of other parts of the CPU.
What is the ALU
Arithmetic Logic Unit - where arithmetic operations and logic operations including AND, OR and NOT are done.
What is Cache?
Slower than registers but faster than RAM. Frequently used programs.
What is a register and what are the 4 types?
Fast memory location in CPU.
Program Counter (PC) - Holds address of next instruction to be executed.
Accumulator (ACC) - Holds the result of an instruction before it is transferred to memory.
Memory Address Register (MAR) - holds memory address of current instruction and data it uses so that these can be fetched from memory.
Memory Data Register (MDR) - holds actual instruction, and then the data that has been fetched from memory. Works in tandem with MAR.
What is the fetch, decode and execute cycle.
- Next instruction and data involved fetched from main memory.
- Instruction decoded.
- Instruction executed.
- Cycle repeats
What happens in the fetch stage of FDE cycle?
Address of instruction to be executed copied from Program Counter –> Memory Address Register
Instruction of that address fetched from memory and copied to Memory Data Register.
What factors affect CPU performance?
Clock speed, No of Cores, Cache size
How does clock speed affect cpu?
Is cycles per second measured in hz. Faster clock speed means faster processing of instructions.
How does No of cores affect Cpu?
Multi core processors mean more instructions can be processed and executed at the same time. However some software can not take advantage of all cores so may not be as fast as some programs designed to only run on one core.
How does cache size affect CPU?
Cache is small, fasrt and expensive memory. It is closer to processer than RAm so takes less time to retrieve an instruction or data. Frequently used programs are stored in here.
Describe the 3 levels of cache memory
Level 1: extremely fast but small (2-256kb). Each core
Level 2: slower than level 1 (256kb - 8mb). Each core
Level 3: slowest but faster than RAM (4mb - 50mb). Cache shared between all cores on processor
What is an embedded system?
Computer system built into larger machine and provides means of control. Single microprocessor including RAM, ROM and CPU. Performs specific tasks.
What are examples of an embedded system?
Washing machine, Traffic light, Cruise control + Engine fan (in cars), Satnav, Microwave and Dishwasher
Compare the following characteristics between and embedded and general purpose machine:
CPU speed, Software, Where Storage occurs + Reliability
CPU speed: Slow on embedded. Very fast on general purpose.
Software: One purpose for embedded system. New software can be installed on general purpose.
Storage: Programs stored on ROM in embedded system. programs stored on hard drives.
Reliability: Embedded more reliable. General purpose less reliable.
What is primary storage?
Needed to store programs that are currently running and need to be accessed by the CPU.
What is RAM?
Random Access Memory (RAM): Often refered to as main memory. Can be read from and writte to. Faster than hardrive. CPU can access any part of the memory in the same amount of time.
Normally stores: OS, software currently in use and the data the software is currently using.
Volatile - data lost if power is off.
How does RAM work?
When computer turned on, RAM empty. OS from hard drive is loaded into RAm. Applications and programs are copied into RAM from hardrive.
What are key features of Secondary Storage?
Not directly accessible by CPU
Non Volatile
Secondary Storage devices may be internal or external to the computer
What are the uses of secondary storage?
Programs are stored on hard drives
Blu-Rays
Memory sticks
Magnetic tape/ external hard drives (for backup)
SD cards - additional storage on cameras/ smartphones
What are the types of primary storage?
RAM and ROM
What are the types of Secondary Storage?
HDD - Hard Disk Drive
SSD - Solid State Drive
