CS1 - Systems architecture Flashcards
CPU
Central Processing Unit; processes instructions in a computer.
Fetch-Execute Cycle
Process of retrieving and executing instructions.
MAR
Memory Address Register; holds address of data to access.
MDR
Memory Data Register; stores data being transferred.
Program Counter
Register that tracks the next instruction’s address.
Accumulator
Register that stores intermediate arithmetic results.
ALU
Arithmetic Logic Unit; performs arithmetic and logic operations.
CU
Control Unit; coordinates CPU operations and instruction flow.
Cache
Fast memory for frequently accessed data and instructions.
Registers
Fast storage locations within the CPU for quick access.
Input Devices
Hardware that allows user input into the system.
Output Devices
Hardware that conveys information from the system.
Main Memory
Primary storage for data and instructions in use.
Secondary Storage
Non-volatile storage for data not in use.
Stored Program Concept
Idea of storing program instructions in memory.
Processing
Execution of instructions by the CPU.
Computer Systems
Integrated hardware and software for processing data.
Human Brain Comparison
CPU compared to brain; both process information.
Billions of Instructions
CPU executes billions of instructions per second.
Von Neumann Architecture
Design model for stored-program computers.
Early Computers
Used switches or punch cards for instruction input.
Mathematician Von Neumann
Pioneered the stored-program concept in computing.
Von Neumann architecture
Program instructions and the data the programs are using are both stored in the same memory.
Control Unit
The control unit coordinates and controls all of the activities taking place within the CPU.
Arithmetic-Logic Unit (ALU)
The ALU or Arithmetic Logic Unit is where the actual arithmetic operations are done.
Program Counter (PC)
Holds the address of the next instruction to be executed.
Memory Address Register (MAR)
Holds the memory address of the current instruction, and then the data that it uses, so that these can be fetched from memory.
Memory Data Register (MDR)
Holds the actual instruction, and then the data that has been fetched from memory.
Fetch - Decode - Execute
The CPU operates by repeating three operations: FETCH, DECODE, and EXECUTE.
FETCH
Causes the next instruction and any data involved to be fetched from main memory.
DECODE
Decodes the instruction.
EXECUTE
The instruction is executed.
MAR and MDR
In the FETCH stage of the F-E cycle, the MAR holds the address of the instruction, and the MDR holds the fetched instruction.
PC increment
The Program Counter is incremented (increased by 1) as soon as that instruction has been fetched.
RAM
Random Access Memory.
ALU operations
Carries out logical operations such as those including AND, OR and NOT.
Example - Step 1 (Add 8 + 4)
PC points to next instruction in location 5, address 5 is passed to MAR and PC is incremented.
Accumulator (ACC)
Stores intermediate arithmetic and logic results.
Arithmetic Logic Unit (ALU)
Performs arithmetic and logic operations.
Instruction Fetch
Retrieves instruction from memory to MDR.
Instruction Decode
Interprets fetched instruction for execution.
Instruction Execute
Carries out the decoded instruction’s operation.
Data Transfer
Moves data between registers and memory.
Step 2 Example
PC points to instruction at location 6.
Step 3 Example
PC points to instruction at location 7.
LDA Instruction
Loads data from memory into the accumulator.
ADD Instruction
Adds immediate value to accumulator’s content.
STO Instruction
Stores accumulator’s value into specified memory location.
Special Registers
Includes PC, MAR, MDR, and Accumulator.
Purpose of CPU
Fetches and executes instructions from memory.
Incrementing PC
PC is increased after fetching an instruction.
Value Transfer
Transfers result from accumulator to memory.
Instruction Cycle
Consists of fetch, decode, and execute phases.
Control Signals
Directs operation of CPU components during execution.
Data Bus
Pathway for data transfer between CPU and memory.
Secondary storage
Not directly accessible by the CPU and is non-volatile, meaning it will keep data even if there is no power.
RAM
A type of primary storage with a fast data rate but is volatile (the data is lost if there is no power).
ROM
A type of primary storage that is non-volatile and retains data even when power is turned off.
Volatile
Data is lost when power is turned off.
Non-volatile
Data is not lost when power is turned off.
1 Terabyte (TB)
Equivalent to 1000 Gigabytes.
Capacity
How much data can be stored - e.g. 700 MB, 50 GB or 2 TB.
Speed
The rate (usually in MB/s) at which data can be read or written.
Portability
How easy it is to carry - is the device small?
Durability
Will the device break if dropped? How well does it work with extreme temperatures or magnetic fields?
Reliability
How likely is the data (or some of it) to be lost?
Cost
What is the cost of a device? How much is it to store 1 MB of data?
Hard Disk Drive (HDD)
A type of secondary storage that has a very large storage capacity, up to 6TB or more.
Solid State Drive (SSD)
Uses non-volatile flash memory to store information with very fast read/write speeds.
Optical storage
Data is stored as pits and lands burnt or pressed into a spiral track circulating outwards from the centre.
Magnetic storage
Uses mechanical parts to read and write data magnetically.
Flash memory
Low cost, portable, no moving parts, durable, ideal for a range of offline devices.
CD-ROM
Has a capacity of up to 720 MB.
DVD
Has a capacity of up to 8.4 GB (dual layered disk).
Blu-Ray
Has a capacity of up to 50 GB (dual layered disk).
Magnetic tape
A type of offline secondary storage used for backup.
USB flash drive
A portable storage device that uses flash memory.
SD card
A type of removable storage used in cameras and smartphones.
Tape drive
A type of storage device that uses magnetic tape to store data.
Floppy disk drive
An older type of storage device that uses floppy disks.
SSD drive
A type of solid state storage device with no moving parts.
Durability of magnetic storage
An issue due to lots of mechanical parts and sealed units.
Data capacity calculation
If we wish to store 5000 photos and each photo has a file size of 10 MB, we need a total of 50 GB.
Primary Storage
Needed to store programs that are currently running and need to be accessed by the CPU.
RAM
Random Access Memory, often referred to as main memory, primary memory, or primary storage, can be read from and written to.
ROM
Read Only Memory, used to store data that needs to be permanently held in primary storage, even when a computer has no power.
Volatile Memory
Memory that loses its data when the power is turned off, such as RAM.
Non-volatile Storage
Storage that does not lose data when the power is off, such as data stored on a hard drive.
Virtual Memory
Part of the hard drive used as an extension to RAM.
Bootstrap
The initial program that is run when the computer is turned on, stored in ROM.
BIOS
Basic Input/Output System, stored in ROM, controls basic technical configuration of the computer.
Memory Speed
The speed that data can be accessed changes through the different components in a computer.
CPU Registers
Small amounts of storage available directly in the CPU for quick data access.
Cache
A smaller, faster type of volatile memory that provides high-speed data access to the CPU.
Operating System
Software that manages computer hardware and software resources and provides common services for computer programs.
RAM Capacity
Typically, a modern personal computer will have 8-32 GB of RAM available.
Advantages of Virtual Memory
Uses cheap secondary storage on the hard drive and prevents error messages saying ‘out of memory’.
Disadvantages of Virtual Memory
Accessing virtual memory is very slow, as existing data in RAM needs to be copied to virtual memory before accessing.
Data Loss in RAM
Data stored in RAM is lost when the computer is turned off.
Access Speed of RAM
Access to RAM is much faster than a hard drive.
Data in ROM
Data is read from ROM but cannot be written to it.
RAM Usage
The computer stores running programs and data in RAM when your computer is turned on.
Filling Up RAM
When RAM completely fills up, the computer may need to use virtual memory.
Difference between RAM and ROM
RAM can be written to, while ROM cannot; RAM is volatile, and ROM is non-volatile.
Cache
Fast memory in CPU for quick data access.
Clock Speed
Speed of CPU operations, measured in hertz (Hz).
Cores
Duplicate processing units in a CPU.
Control Unit (CU)
Decodes instructions and controls CPU timing.
Arithmetic Logic Unit (ALU)
Performs arithmetic and logic operations.
Registers
Small storage locations for CPU data.
Program Counter (PC)
Register that tracks the next instruction.
Memory Address Register (MAR)
Holds memory location of data to fetch.
Memory Data Register (MDR)
Holds data retrieved from RAM.
Accumulator (ACC)
Stores results from the ALU operations.
Multi-core Processor
Processor with multiple cores for simultaneous tasks.
Dual-core Processor
Processor with two cores for parallel processing.
Quad-core Processor
Processor with four cores for enhanced performance.
Level 1 Cache
Fastest cache, 2-256KB, per core.
Level 2 Cache
Fast cache, 256KB-8MB, per core.
Level 3 Cache
Slowest cache, 4MB-50MB, on CPU.
Cycles per Second
Measured in hertz; indicates instruction speed.
1 Hertz (Hz)
One cycle per second; one instruction executed.
1 Kilohertz (kHz)
1,000 cycles per second.
1 Megahertz (MHz)
1,000,000 cycles per second.
1 Gigahertz (GHz)
1,000,000,000 cycles per second.
Cache Memory
Stores frequently used data for quick access.
Embedded Systems
Specialized computing systems within larger devices.
CPU Performance Factors
Clock speed, cores, and cache size influence performance.
Number of Cores
Processing units available in a CPU.
Embedded System
Computer system for controlling devices.
Embedded Computer
Single microprocessor with RAM, ROM, and CPU.
Reliability of Embedded Systems
Typically very reliable, fewer bugs than general systems.
General Purpose Machine
Can run multiple software programs.
Storage in Embedded Systems
Programs stored on ROM, not hard drives.
Examples of Embedded Systems
Satnav, microwave, dishwasher, burglar alarm.
Car Embedded Systems
Control functions like cruise control and lighting.
Performance Ranking
Based on clock speed and cache size.
CPU Wait Time
Reduced by using cache memory effectively.
Dual Core Processor
Two processing units in a single CPU.
Quad Core Processor
Four processing units in a single CPU.
Processor GHz
Frequency indicating processing speed.
Embedded Functions in Cars
Examples include engine control and infotainment.
Digital Device Functionality
Dependent on embedded systems for operations.
Main Memory
Slower than cache, used for data storage.
Infotainment Systems
Provide entertainment and navigation in vehicles.
Engine Control Unit (ECU)
Manages engine performance and efficiency.
