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Lecture 1 - Final Example - Working out CPU B instruction percentage

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Lecture 1 - Final Example - Working out CPU B instruction percentage Empty Lecture 1 - Final Example - Working out CPU B instruction percentage

Post  Alex on Tue Oct 09, 2012 3:45 am

In the example there is a part which says 'For CPU B, 25% of all instructions are branches (you need to work this out)'

Here's the working (I think):

CPU A
From the question we know 20% of all instructions are bne
Since the way the CPU works, every bne requires a cmpr before it
So another 20% of instructions will be cmpr

This leaves us with: 20% bne, 20% cmpr, 60% other

CPU B
In this CPU, the bne and cmpr instructions are merged, merging the percentages of CPU A gives us
20% bne/cmpr, 60% other

Obviously that doesn't total 100% so we need to 'extend' the percentages
20x + 60x = 100
x = 5/4

Therefore the percentage of instructions which are bne/cmpr = 5/4 * 20 = 25%
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Post  ElliottH on Tue Oct 09, 2012 3:59 am

Okay I was being very lazy with note taking as it's the first day back, what were these abbreviations again? Very Happy
I got MIPS = Microprocessor without Interlock Pipeline Stages
and RISC = Reduced Instruction Set Computer
but missed/fell asleep for the others
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Post  Alex on Tue Oct 09, 2012 4:53 am

Afaik only one you are missing is DLX which we only told was an educational version of MIPS (according to wikipedia it stands for Deluxe)
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