computer organization

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computer organization

Postby raj2014 » Wed Jan 15, 2014 3:34 am

which of following data dependency tackling techniques may not always avoid data dependency?
a)stall cycle
b)Noop
c)rescheduling technique
d)operand forwarding

plz justify ur ansr
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Re: computer organization

Postby sameer2009 » Sat Jan 18, 2014 10:39 am

resheduling

ADD R1, R2, R3 ....R1 = R2 + R3
MUL R2, R1, R3 ....R2 = R1 * R3
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Re: computer organization

Postby Unnikuttan » Wed Feb 05, 2014 12:36 pm

sameer2009 wrote:resheduling

ADD R1, R2, R3 ....R1 = R2 + R3
MUL R2, R1, R3 ....R2 = R1 * R3


@Sameer..

I'm a little confused here...."Rescheduling" is rearranging the instructions ...right..?

rearranging the instructions may not always yield a correct solution isn't it..? suppose if all instructions in the program are dependent..then..? here is it is possible to avoid data dependency using stall cycle only...or we can have the operand forwarding too..

Is operand forwarding always work..?

I guess stall cycle will do in all the cases...

Please advice..

Unni.
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Re: computer organization

Postby sameer2009 » Thu Feb 06, 2014 12:09 pm

Unnikuttan wrote: I'm a little confused here...."Rescheduling" is rearranging the instructions ...right..?

rearranging the instructions may not always yield a correct solution isn't it..? suppose if all instructions in the program are dependent..then..? here is it is possible to avoid data dependency using stall cycle only...or we can have the operand forwarding too..
Is operand forwarding always work..? NO

I guess stall cycle will do in all the cases...

Please advice..

Unni.

yes correct..


Does the example which i gave falls in rearrangement?

or ...does rescheduling means starting an instruction after its specified time...say if an instr "I" is scheduled to start at t=3 and if data dependency is identified then "I" and all inst after I are delayed by some amount of time....rescheduled "after a delay"
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Re: computer organization

Postby Unnikuttan » Fri Feb 14, 2014 11:01 pm

sameer2009 wrote:
Unnikuttan wrote: I'm a little confused here...."Rescheduling" is rearranging the instructions ...right..?

rearranging the instructions may not always yield a correct solution isn't it..? suppose if all instructions in the program are dependent..then..? here is it is possible to avoid data dependency using stall cycle only...or we can have the operand forwarding too..
Is operand forwarding always work..? NO

I guess stall cycle will do in all the cases...

Please advice..

Unni.

yes correct..


Does the example which i gave falls in rearrangement?

or ...does rescheduling means starting an instruction after its specified time...say if an instr "I" is scheduled to start at t=3 and if data dependency is identified then "I" and all inst after I are delayed by some amount of time....rescheduled "after a delay"


here rescheduling, what I meant is inserting INDEPENDENT instruction between dependent ones...but if Independent instructions are not available then nothing will help ...

Here I think none of the techniques are helpful in avoiding the data dependency completely...

Unni
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