1.1 Systems Architecture Flashcards
How many times per second does the fetch-decode-execute cycle happen?
Billions of times per second.
What are two events that take place during the execute stage?
- Performing calculations
- Storing a result in memory
What are the four key components of the CPU?
- ALU
- Control unit
- Cache
- Registers
What two things does the control unit do?
- Controls the flow of data and instructions around the CPU.
- Decodes instructions fetched from memory.
What does the Program Counter (PC) do?
Holds the memory address of the next instruction.
(Explain) Why doesn’t an embedded system need virtual memory? (2)
- There is enough space in RAM.
- Only a small amount of data is stored in RAM
When talking about embedded systems, what keyword do you need to remember?
Dedicated (hardware)
What does the MAR do?
Holds the memory address of where data or instructions are to be fetched from.
What are registers?
Small amounts of high-speed memory (in the CPU) that can hold one instruction at a time.
What does the MDR do?
Stores the data (or instruction) which has been fetched from memory.
What are two functions of the CPU?
- Fetch instructions from memory
- Decodes and executes instructions
What are two additional features of embedded systems?
- Limited OS
- Simple user interface
What is cache?
Small, fast access memory close to the CPU which stores frequently used data and instructions.
Explain one reason why the cache size affects the performance of the CPU. [2] (What keyword do you need to remember?)
It’s faster to transfer to and from cache compared to RAM.
(Keyword = Faster)
Identify four events that take place during the fetch-execute cycle. [4]
- CPU fetches an instruction from memory
- Instruction is decoded
- The decoded instruction is executed
- Process repeats
An embedded system is a computer system built into a ___ ___.
larger machine.
What are three other embedded systems apart from a sat nav?
- Washing machine
- Microwave
- Dishwasher
What does a clock speed of 3.8 GHz mean? [2]
3.8 billion instructions per second.
“If you double the number of cores, the computer will run twice as fast.” Why isn’t this statement always true? [3]
- The speed of is affected by other factors, such as cache size, clock speed or RAM.
- If the cores aren’t parallel processing, then there’s no need for multiple cores.
Dual core =
Parallel processing
Cache =
(3 words)
SmallC
Faster
Frequently used
Control unit =
- Co-ordinates + controls operations
What is the purpose of the CPU? (FDE)
Performs the fetch-decode-execute cycle.
