Exam style questions
What is meant by the Von Neumann architecture? (1 mark)
Data and instructions are stored together in the same memory.(1)
What actions occur at each stage of the fetch-execute cycle? (3 marks)
At the fetch stage the next instruction is fetched from main memory or cache. (1) At the decode stage the binary instruction is decoded to see what action the CPU needs to perform. (1) At the execute stage the instruction is carried out. (1)
Explain what cache is and how it can improve the performance of a CPU. (4 marks)
Cache is a small but superfast piece of memory (1) that stores recently and freuently used data and instructions.(1) When the processor wants some data or an instruction it first looks for it in the cache and if it is found
it is returned faster than accessing it from RAM (1) and if it is not found then a copy is placed in the cache on the way back from RAM making it faster to fetch next time. (1)
MAR: Address (1) MDR: Data (1) Program counter: Address (1) and Accumulator: Data (1)
Explain the role of the memory data register during the fetch decode execute cycle. (2 marks)
The MDR temporarily stores the instruction that is returned from the address in RAM specified by the MAR (1) and any data that is returned by RAM to be used with that instruction (1)
CPU specifications
Jim likes to play games on his computer. Sometimes he will be researching online while listening to music and having open a couple of documents he is working on. He wants the most powerful computer he can get. He has got it down
to a choice of 3. The specifications for their CPUs are above. Explain how the three factors shown affect CPU performance and explain which to choose and why. (5 marks)
Clock speed measured inGhz is the number of instructions it can process per second with more being better.(1) Cores are effectively seperate processors. A dual core means there are two and a quad core means there are 4.(1)
Cache is a small fast area of storage for regularly used and recently used instructions and data. Having more speeds up processing.(1) Although the first computer has the highest clock speed the others have multiple cores and
in total execute more instructions (4.8GHz).(1) As they can complete the same number of instructions it comes down to cache and so the dual core would be best.(1)
Explain what an embedded system is and give an example of one. (2 marks)
An embedded system is a basic computer system built into another device(1); Any suitable example of an inbuilt single purpose computer e.g. toaster, microwave(1)
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