Computer Architecture - short answer type questions from AMIE exams (Summer 2021)

Answer the following questions (2 marks each)

What is ‘Cycle Stealing’? Explain.

  • Cycle stealing is a method of accessing computer memory (RAM) or bus without interfering with the CPU. It is similar to direct memory access (DMA) for allowing I/O controllers to read or write RAM without CPU intervention.
  • This is similar to Burst Transfer mode, but instead of the data being transferred all at once, it is transferred one byte at a time.
  • In this method, the transfer rate is slower but it prevents the CPU from staying idle for a long period of time.

How many minterms are there if a truth table with n number of variables? Give example.

There are 2n min-terms of n variables since a variable in the min-term expression can be in either it's direct or its complemented form—two choices per variable.
Example: In a 2 variable function how many minterms are there?
2² = 4 min-terms possible.

Which of the shift operation divide a signed binary number by 2? Show that using an example.

Logical right shift. When shifting right with an arithmetic right shift, the least-significant bit is lost and the most-significant bit is copied.

‘In a J-K flip-flop the function K = J’ is used to realize T flip-flop’ justify.

T flip-flop allows the same inputs. So, in J-K flip-flop J=K then it will work as T flip-flop.

What logic circuit would you use for addressing memory?

Decoder. to give each program full address space even though actual memory is much lesser and to protect one program from modifying data of another program, Virtual memory is implemented. So, memory address decoding is required.

What is the difference between horizontal and vertical microinstructions?

Vertical microprogramming employs a variable format and a higher degree of encoding, as opposed to horizontal microprogramming. In vertical microprogramming, the control bits are encoded with each code being used for each action to be performed and an instruction decoder decodes the code into multiple control signals. On the contrary, horizontal microprogramming involves horizontal microinstructions that use no encoding at all. 

What do you mean by temporal and spatial locality of cache memory?

Spatial Locality
Spatial Locality means that all those instructions which are stored nearby to the recently executed instruction have high chances of execution. It refers to the use of data elements(instructions) which are relatively close to storage locations.

Temporal Locality
Temporal Locality means that an instruction which is recently executed has a high chance of execution again. So the instruction is kept in cache memory such that it can be fetched easily and takes no time in searching for the same instruction.

What is the difference between instruction dependency and data dependency in pipelining?

A position in which an instruction is dependent on a result from a sequentially earlier instruction before it can be done its execution. In high-performance processor operating pipeline or superscalar techniques, a data dependency will learn an interruption in the flowing services of a processor pipeline or prevent the parallel issue of instructions in a superscalar processor.

What is called instruction-level parallelism?

Instruction-level parallelism (ILP) is a measure of how many of the operations in a  computer program can be performed simultaneously. The potential overlap among instructions is called instruction-level parallelism.

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