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Microprogrammed control unit:

1. is faster than a hardwired control unit
2. facilitates easy implementation of new instructions
3. is useful when very small programs are to be run
4. usually refers to control unit of a microprocessor

retagged | 3.1k views

1. is wrong. Microprogrammed CU can never be faster than hardwired CU. Microprogrammed CU it has an extra layer on top of hardwired CU and hence can only be slower than hardwired CU.

2. is a suitable answer as we can add new instruction by changing the content of control memory.

3. is not correct as when only small programs are there, hardwired control makes more sense.

4. control unit can also be hardwired, so this is also not correct.

Correct Answer: $B$

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Why not d?
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@Arjun sir

Is it because only few hardware devices are needed. And in Case of Microprogrammed, circuit complexity remains same for small programs too.

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Hardwired is faster than mircroprogrammed (but less flexible). If program size is small and won't be modified, hardwired is preferred.
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@Arjun Sir

above reference link is not working...

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I cannot really understand the relation between  the length of programs and the use of hardwired/microprogrammed control units.

if we have only small length of programs then  will have less complexity of the hardwired circuit.because of less number of instructions.

but having small length programm doesnot guarantee us that we will have less number of instructions .In total we might have a large number of different  instructions.(making the circuit complex )

if we have large length programs then we will have more complexity  of the  hardwired circuit.because of more number of instructions.

but having large length program doesnot guarantee us that we will have large number of instructions .In total we might have a programs using only a small set of instructions.thus less hardwire required.

so the length of program doesnot determine the which type of control unit to use.