Awesome q2a theme
0 votes
37 views
Consider the cache memory that is 30 times faster than main memory and used 90% of the total time. What is the speedup gain by the cache memory?
in CO & Architecture by (13 points) | 37 views

1 Answer

+1 vote
Best answer

Speedup will be 7.69

Direct application of Amdahl's Law - https://www.geeksforgeeks.org/computer-organization-amdahls-law-and-its-proof/

$Speedup = (1 - 0.9 + \frac{0.9}{30})^{-1} = 7.69$

by (1.9k points)
selected by
0

@shashin1989 Sir, if we consider it as this: Let it takes x cycles to access memory, hence x/30 cycles to access the cache ,hence, AMAT in case of this cached organization is 0.90*(x/30)+0.10*(x+x/30) and in case of memory organization it takes x cycles only. Then by taking their ratio I got 7.50 as answer....can you tell where am I going wrong?:(

0

@Deterministic I don't think you need need to do (x+x/30) instead it should only be x because execution for the rest 10% will remain the same.

0

@Pratyush Priyam Kuan in case of a cache miss we also need to take into account the cache access time..as we only get to know that we have a miss after we access the cache... correct me if I am wrong..

0
Question is asking about the speedup in a theoretical system where part of it has some enhancement. Why are you taking into account cache misses and other factors ?

If half of the road from Delhi to Agra is a new highway that lets you drive at twice the speed limit - and somebody asks you what is the time improvement in driving from Delhi to Agra, you won't respond by taking into account traffic jams, cows on the road, etc right ? Same thing here. Question is asking speedup of system with enhancement over system without enhancement. How efficient that enhancement is - is beyond the scope of the question.
0

Thanks @shashin got your point:)

Quick search syntax
tags tag:apple
author user:martin
title title:apple
content content:apple
exclude -tag:apple
force match +apple
views views:100
score score:10
answers answers:2
is accepted isaccepted:true
is closed isclosed:true
Welcome to GATE CSE Doubts, where you can ask questions and receive answers from other members of the community.
Top Users Jul 2020
  1. Shaik Masthan

    39 Points

  2. hiteshpujari

    9 Points

  3. Venkatesh Akhouri

    6 Points

  4. Meghana518

    6 Points

  5. bittujash

    6 Points

  6. Pawan_k

    6 Points

  7. rits78671

    6 Points

  8. srestha

    6 Points

  9. RavGopal

    4 Points

  10. Sumaiyas

    4 Points

7,543 questions
1,783 answers
10,867 comments
90,482 users