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1. cache memory overview

Cache memory is the fast and small memory. The basis idea of using a cache is simple. When CPU need a word, it first looks in the cache. Only if the word is not there does it go to main memory. If a substantial fraction of the words are in the cache, the average access time can be greatly reduced. So the success or faillure thus depends on what fraction of the words are in cache. The idea solution is that when a word is referenced, it and some of its neighbors are brought from the large slow memory into the cache, so that the next time it can be accessed quickly.

  • Improving Performance

The memory mean access time, TM, is considered as follow:

TM = c + (1- h).m

Where:

c : the cache access time

m: the main memory access time

h: the hit ratio, which is the fraction of all references that can be satisfied out of cache (the success of cache), also the miss ratio is 1-h.

  • Cache memory is a critical component of the memory hierarchy.

Figure 10.1. The cache is logically between the CPU and main memory in the the memory hierarchy. Physically, there are several possible places it could be located.

  • Characteristics

– Compared to the size of main memory, cache is relatively small

– Operates at or near the speed of the processor

– Cache is very expensive compared to main memory

– Cache contains copies of sections of main memory

  • Cache is considered as the main memory interface

– Assume an access to main memory causes a block of K words to be transferred to the cache

– The block transferred from main memory is stored in the cache as a single unit called a slot, line, or page

– Once copied to the cache, individual words within a line can be accessed by the CPU

– Because of the high speeds involved with the cache, management of the data transfer and storage in the cache is done in hardware

- If there are 2n words in the main memory, then there will be M=2n /K blocks in the memory

– M will be much greater than the number of lines, C, in the cache

– Every line of data in the cache must be tagged in some way to identify what main memory block it is. The line of data and its tag are stored in the cache.

  • Factors in the cache design

- Mapping function between main memory and the cache

- Line replacement algorithm

- Write policy

- Block size

- Number and type of caches

2. cache organization and operations

Mapping function organization: Mapping functions since M>>C, how are blocks mapped to specific lines in cache

2.1 direct mapping

a/ Organization:

The simplest cache is known as a direct-mapped cache or direct mapping, it is shown in Figure 10.2.

– Direct mapping cache treats a main memory address as 3 distinct fields

+ Tag identifier

+ Line number identifier

+ Word identifier (offset)

– Word identifier specifies the specific word (or addressable unit) in a cache line that is to be read

– Line identifier specifies the physical line in cache that will hold the referenced address

– The tag is stored in the cache along with the data words of the line

Figure 10.2. Direct mapping cache Organization

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Good
When we have data register and address registers in user mode (visible registers) then why we need MAR and MBR
Hassan Reply
with the given example MOV BX,AX describe the sequence that will be followed using instruction state diagram
Gireesh Reply

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Source:  OpenStax, Computer architecture. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10761/1.1
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