GATE CSE 1999 | Question: 2.19

Question

Arrange the following configuration for CPU in decreasing order of operating speeds:

Hard wired control, Vertical microprogramming, Horizontal microprogramming.

• A. Hard wired control, Vertical microprogramming, Horizontal microprogramming.

• B. Hard wired control, Horizontal microprogramming, Vertical microprogramming.

• C. Horizontal microprogramming, Vertical microprogramming, Hard wired control.

• D. Vertical microprogramming, Horizontal microprogramming, Hard wired control.

Comments

Reference : William stalling & Morris Mano 

==> Hardwired control units operate at significantly higher speeds than microprogrammed units because control signals are generated directly by combinational logic circuits. Microprogrammed control requires fetching microinstructions from a control memory, adding a memory read access time to every clock cycle.

==>Horizontal microprogramming provides higher execution speed and parallelism because control bits are minimally encoded and directly control hardware components with little to no decoding delay. Vertical microprogramming uses highly encoded fields that require intermediate decoders, introducing additional logic gate delays and limiting micro-operation parallelism.

 

Answer 1

Hard wired control involves only hardware, whereas microprogramming is software approach. So, hardwire control should be faster than both microprogramming approaches.

Between vertical and horizontal microprogramming. Horizontal is faster because in this control signals are not encoded whereas in vertical microprogramming to save memory signals are encoded. So, it takes less time in horizontal microprogramming because decoding of signals is not required. Therefore, final order is :

hard wired control > horizontal microprogramming > vertical microprogramming

Correct Answer: $B$

Comments

This comes under which topic in GATE Computer Organization subject? Is this in syllabus?

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microprogrammed control unit

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yes its in syllabus

 

Answer 2

Answer: B

Comments

Any reason?

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Explain plzzzzzzzzzzzzzzzzzzz

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This comes under which topic in GATE Computer Organization subject? Is this in syllabus?

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Control unit