1.1 System Architecture

1.1 System Architecture

1. Registers

   • MAR
     • Holds memory address about to be used by the CPU
   • MDR
     • Holds data or instructions that have been fetched from memory
   • Program Counter
     • Holds the memory address of the instruction for each cycle
   • Accumulator
     • Stores the results of the calculations done by the ALU

2. FDE cycle

   • 1.......
   • 2........
   • 3.........
   • 4........

3. Characteristics

   • Clock speed
   • Cache size
   • Number of cores

4. Embedded systems

   • A computer system built into another device (usually designed for a specific purpose)

5. Components

   • ALU (Arithmetic Logic Unit)
     • Performs logical operations (AND, OR, NOT), Shift operations and Arithmetic operations (+,-, *, / )
   • Control Unit (CU)
     • Controls activities in the CPU (Such as flow of data between CPU and other parts) and makes FDE cycle happen in correct order
   • Cache
     • Sits between the CPU and RAM. Very fast. Holds frequently used data so that the processor doesn't have to keep going back and forth to the RAM.

6. Purpose of the CPU

7. Von Neumann architecture

   • Traditional computer architecture that forms the basis of most digital computer systems. Programs and data can be stored in the same memory unit.

8. Harvard architecture

   • Stores programs and data in separate memory units. Entering or altering programs is harder with this method

9. FDE (Fetch Decode Execute) Cycle

10. BIOS

    • Basic Input and Output System. This is the ROM chip on the motherboard that takes care of booting the OS into memory

11. Bootstrap Loader

    • Responsible for loading (Booting) the Operating System into memory

12. Virtual memory

    • This type of memory is for when the computer runs out of available RAM and so uses part of the HDD (Hard Disk Drive) instead. This is not desirable however as the HDD is slower than just using RAM.

13. Volatile

    • Means that when the power is removed then all data is lost.

14. Non volatile

    • Means that when power is removed, data is retained/kept

15. Flash memory

    • This type of memory is solid state (i.e. No moving parts) that retains data even when power is removed. It is used in SSDs and memory cards, for example.

16. Primary storage

    • Sometimes called Main Memory. Refers to the memory areas that the CPU can access very quickly (Cache, RAM and ROM). Primary storage has the fastest read/write speeds and is mostly volatile.

17. Secondary storage

    • Also known as backing storage. This is non-volatile - it's where all data (operating systems, applications and user files) are stored when not in use. Read/write speeds are much slower compared to primary storage.

18. Optical storage

    • A form of storage that uses light/lasers to read and write data (e.g. CD ROM, CD-RW, DVD ROM, Blu-ray)

19. Magnetic Storage

    • A form of storage that uses magnetism to read and write data(e.g HDD, Floppy Disc, Cassette Tape, Magnetic tape)

20. Solid state storage

    • A form of storage that uses flash memory chips to store data(e.g. SSD (Solid State Drive), USB flash memory, SD card). It has no moving parts.

21. Data Capacity

    • A characteristic of secondary storage which means - "How much can the storage device hold?" (usually measured in kb, Mb, Gb, Tb)

22. Speed

    • A characteristic of secondary storage which means - "How fast can data be read/written?" (usually measured in MB/sec)

23. Portability

    • A characteristic of secondary storage which means - "Can you unplug/carry it around easily?"

24. Durability

    • A characteristic of secondary storage which means - "How long is the product expected to function for before it is no longer useable?"

25. Reliability

    • A characteristic of secondary storage which means - "How likely is it that the product will fail in its lifespan?"

26. Cost

    • A characteristic of secondary storage which means - "How expensive is the storage device (per GB)?"

27. ROM

    • (Read Only Memory) is usually a flash memory chip on the motherboard that contains instructions needed to start up (boot) the operating system

28. RAM

    • (Random Access Memory) is a device that can plug into the motherboard. RAM contains programs, instructions and data that are currently being worked on (in use)