Control Unit - Q4

+2 votes

A microprogram control unit is required to generate a total of 10 control signals. Assume that during any micro instruction, at most 5 control signals are active. Minimum number of bits required in the control word to generate the required control signals will be:

(A)10

(B)9

(C)8

(D)7

asked Jun 8 in Computer Organization by gbmentor (54,290 points)
reshown Jun 9 by gbmentor

4 Answers

+1 vote
 
Best answer

total 10 control signal at most 5 active so

total = _{0}^{10}\textrm{C}+_{1}^{10}\textrm{C}+_{2}^{10}\textrm{C}+_{3}^{10}\textrm{C}+_{4}^{10}\textrm{C}+_{5}^{10}\textrm{C} = 638

\lceil \log_2 (638)\rceil = \lceil 9.317 \rceil= 10

So the option is A

 

answered Jun 9 by 23rishiyadavpro20 (6,590 points)
selected Jun 9 by getgatebook
https://gateoverflow.in/2754/gate1996-2-25
Just See this question. If we try in this way we are not getting the correct answer.
actually for that 9 bits is the correct answer although there is no appropriate option so there assumed 5X32 and 5X32 decoder assumed in that way 10 bits
but in this question, I am getting option
Yes you might be right. But what is wrong with that approach( only disadvantage is  that we are not getting the answer). But question should be made in such a way that with any approach we should be getting the same answer.

With your approach they have to assume 9 bits answer as 10 bits but they all are getting exact answer without assuming anything with that approach.
It's same like that if we ask you to for 513 how may minimum bit required to represent in binary than answer is 10 but if option given

11
12
8
7
Than every one select 11
Because in given option best one is 11 but it is not minimum best is 10

Same here minimum is 10 because option otherwise minimum is 9 with the help of other concept.which one explain by Rishi Yadav.
This is an ideal approach you should follow if that option is not present go for the option which is near
+1 vote

@getgatebook

This question might be wrong because the answer to this question is not given in the options.

\\ Total\ control\ signals=10\\ Number \ of\ bits=\log _{2}10=4\\ We\ assumed\ vertical\ microprogramming\ as\ minimum\ number\ of\ bits\ is\ asked\\ Atmost\ 5\ control\ signals\ active \\ \therefore Minimum\ number\ of\ bits\ required\ in\ the\ control\ word=5*4=20\ bits

answered Jun 9 by tskushagra-guptacse (11,420 points)
0 votes
A is correct one only 10 bit at most 5 mean

Only 1+ only 2 + only 3 + only 4 + only 5

10+45+120+210+252=667 so total bit used

With decoder is log 667= 10 bit.
answered Jun 9 by tsnikhilsharmagate2018 (19,690 points)
+1 vote
answered Jun 9 by tsnikhilsharmagate2018 (19,690 points)
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