1.1 System Architecture Flashcards
Hardware
Physical stuff in a computer system, e.g. CPU, keyboard, etc.
Software
Programs that a computer system runs, e.g. operating systems, games, etc.
Embedded systems
Computers built into other devices, usually as control systems. E.g. Dishwashers, microwaves.
- Easier to design
- Cheaper to produce
- More efficient at their task than general-purpose systems
What are the four common CPU components?
- Control Unit (CU)
- Arithmetic Logic Unit (ALU)
- Cache
- Registers
Central Processing Unit (CPU)
Where a computer processes all data and instructions
Control Unit (CU)
Controls the flow of data in and out of the CPU. Manages the fetching, decoding and execution of instructions
Arithmetic Logic Unit (ALU)
Does basic calculations, binary shifts and logic operations
Cache
Stores regularly use data for quick access. Low capacity and expensive. 3 levels of cache memory: L1 -> L3, decreasing speed but increasing capacity
Registers
Temporarily hold small amounts of data. Very quick to read/write to
What are the 3 factors affecting CPU performance?
- Number of cores
- Clock speed
- Cache size
How does the number of cores affect CPU performance?
- Each core process data independently
- More cores -> more instructions carried out per second
- Some software takes advantage of multicore processing
How does clock speed affect CPU performance?
Number of instructions a single processor core can carry out per second
How does cache size affect CPU performance?
Larger CPU cache -> faster access to more data
What is in the Von Neumann Architecture?
- Control unit -> Program counter (PC)
- Arithmetic Logic Unit -> Accumulator
- Registers -> Memory Address Register (MAR) and Memory Data Register (MDR)
- Memory
- Input and output device
Program Counter (PC)
Holds the memory address of the instruction for each cycle
Memory Address Register (MAR)
Holds any memory address about to be used by the CPU. The address could point to data or an instruction
Memory Data Register (MDR)
Holds the actual data or instruction, either fetched from memory or waiting to be written to memory
Accumulator
Stores intermediate results of calculations in the ALU
Fetch (FDE cycle)
- Memory address copied from the PC to the MAR
- Instruction copied from memory to the MDR
- PC incremented to point to the next instruction
Decode (FDE cycle)
- Instructions in the MDR decoded by the CU
- CU prepares for the next step, e.g. loading values into the MAR or MDR
Execute (FDE cycle)
Decoded instruction carried out. E.g.
- Load data from memory
- Write data to memory
- Do calculation or logic operations (using the ALU)
Primary storage
Memory that the CPU can read/write to quickly, e.g. RAM
Volatile
Power is required for the component to retain data
Non-volatile
Component retains the data even when the power is turned off
Random Access Memory (RAM)
The main temporary memory in a computer
- Volatile memory
- Can be read from and written to
- Programs and files are copied here from secondary storage while in use
- Slower than the CPU cache, but faster than the secondary storage
Virtual Memory
- Used when RAM is filled up
- Some data is moved to a location in secondary storage
- Data is moved back to RAM when the CPU needs it
- Data transfer is slower on secondary storage -> slows performance
Read Only Memory (ROM)
Main permanent memory in a computer
- Non-volatile memory
- Can only be read from, not written to
- Small amount of memory built into the motherboard
- Contains BIOS (Basic Input Output System) -> instructions needed for the computer to boot up
Secondary Storage
Non-volatile storage where programs and data are kept for later use
Examples of internal storage
- Optical Disk Drives (ODDs)
- Hard Disk Drives (HDDs)
- Solid State Drives (SSDs)
Hard Disk Drives
- High capacity
- Quick access to data
- Moving parts -> will eventually fail
- Stores data magnetically on metal disks
- Can be noisy
Solid State Drives
- Medium capacity
- Very quick access to data
- No moving parts
- Use flash memory for faster read/write times
- Usually quiet/silent
Examples of external storage
- Flash drives & memory cards
- Optical discs
- Magnetic tape
- External HDDs & SSDs
Flash drives & memory cards
Solid-state storage used to expand the capacity of small devices
Optical discs
e.g. CDs. Can be read-only, write-once or rewritable
Magnetic tape
Used by organisations to store huge amounts of data
External HDDs & SSDs
Portable versions of internal storage. Often used for backups
What are the 5 functions of an operating system (OS)
- Peripheral management and drivers
- Providing a user interface
- Memory management and multitasking
- File and disk management
- User management
Peripheral management and drivers
- Communicate either internal hardware and peripherals connected to the system, using drivers
- Chooses correct drivers for connected hardware on startup
- Installs drivers for new hardware and update drivers automatically
Providing a user interface
Allows user to interact with a computer. Different interfaces are designed for different types of user:
- Graphical User Interfaces (GUIs) -> windows, icons, menus and pointers. Designed for everyday users
- Command-Line Interfaces -> text-based and use fewer system resources than GUIs. Used by advanced users
