Topic 2 - Computer Architecture Flashcards
Fetch
- The program counter (PC) holds the memory address of the next instruction that is going to be read/written to
- The address is transferred to the MAR via the address bus
- The MAR sends the memory address to RAM via the address bus to signal it to read the instruction at the specified memory address
- The instruction is sent to the MDR via the data bus from the RAM and then copied into the CIR (Current Instruction Register) also via the data bus
- The PC is incremented to the next instruction
Decode
- Th UI interprets and decodes the instruction in the CIR
Execute
- The ALU carries out the decoded instruction by performing arithmetic or logical operations
- The ACC stores and accumulates the result of the calculations performed by ALU if needed.
ROM
Read only memory that stores the permanent and persistent instructions to boot up the computer (BIOS)
Cache memory is more _____ than RAM and is checked before/after the RAM
expensive
before
Secondary Memory relationship to CPU
It is not directly connected to CPU unlike primary memory
Virtual Memory
This is utilized when primary memory is overloaded. It works by sending less used data from primary memory to secondary memory in pages freeing up space in the primary memory. When primary memory needs the data sent again, it is sent back to the primary memory from secondary memory.
Virtual memory 2 characteristics
- Slower
- Temporary
Draw VM diagram
2 boxes next to each other with a gap in between
1 box = RAM
1 box = Hard disk (but secondary box inside it called Virtual memory (pagefile))
There are two arrows that connect the boxes.
One arrow on the top going from RAM to hard disk called “less used data”
One arrow under it going from hard disk to RAM called “data needed by the CPU”
Operating system definition
Set of software that controls computer’s hardware and resources and provides services for computer programs
3 examples of roles of OS
- User interface
- Memory management
- Multitasking
User interface
It is what facilitates the link between user and hardware
4 examples of UI
GUI
CLI
Natural LI (speak to computer like Siri)
MBI (like CLI but no commands only menu options)
Memory management
A role of OS. It refers to keeping tracking of storage devices, allocating the appropriate amount of RAM to programs in use and organizing and managing data files and folders.
Peripheral management
A role of OS. The OS works with the BIOS and device drivers to translate signals from peripherals into instructions the system can understand and use.
