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» Extremely fast for large memory sizes

» Cost per bit is 5-10 times that of a “normal” RAM cell

» Example: some cache memory units.

2. types of memory

Computer memory system consists a various types of memory. Manufactures produce a number of different types of memory devices having a variety of technologies. The technology affect not only the operating chracteristics but also the manufacturing cost. In the section following we present an overviews of types of memory. You can see the study in detail of memory in the modules 10, 11 and 12.

  • Main Memory (“Internal” memory components)

- RAM (read-write memory): Static RAM, Dynamic RAM

- ROM (Read Only Memories) : ROMs, PROMs, EPROMs, EEPROMs, Flash Memory.

  • Cache memory

The cache memories are high-speed buffers for holding recently accessed data and neighboring data in main memory. The organization and operations of cache provide an apparently fast memory system.

  • External Memory

- Magnetic disks

- RAID technology disks

- Optical disks

- Magnetic tape

3. memory hierarchy

3.1 memory system organization

No matter how big the main memory, how we can organize effectively the memory system in order to store more information than it can hold. The traditional solution to storing a great deal of data is a memory hierarchy.

  • Major design objective of any memory system:

– To provide adequate storage capacity at

– An acceptable level of performance

– At a reasonable cost

  • Four interrelated ways to meet this goal

– Use a hierarchy of storage devices

– Develop automatic space allocation methods for efficient use of the memory

– Through the use of virtual memory techniques, free the user from memory management tasks

– Design the memory and its related interconnection structure so that the proces

3.2 multilevel memories organization

Three key characteristics increase for a memory hierarchy. They are the access time, the storage capacity and the cost. The memory hierarchy is illustrated in figure 9.1.

Figure 9.1. The memory hierarchy

We can see the memory hierarchy with six levels. At the top there are CPU registers, which can be accessed at full CPU speed. Next commes the cache memory, which is currently on order of 32 KByte to a few Mbyte. The main memory is next, with size currently ranging from 16 MB for entry-level systems to tens of Gigabytes. After that come magnetic disks, the current work horse for permanent storage. Finally we have magnetic tape and optical disks for archival storage.

  • Basis of the memory hierarchy

– Registers internal to the CPU for temporary data storage (small in number but very fast)

– External storage for data and programs (relatively large and fast)

– External permanent storage (much larger and much slower)

Figure 9.2 Typical Memory Parameters

  • Characteristics of the memory hierarchy

– Consists of distinct “levels” of memory components

– Each level characterized by its size, access time, and cost per bit

– Each increasing level in the hierarchy consists of modules of larger capacity, slower access time, and lower cost/bit

4. memory performance

Goal of the memory hierarchy. Try to match the processor speed with the rate of information transfer from the lowest element in the hierarchy.

  • The memory hierarchy speed up the memory performance

The memory hierarchy works because of locality of reference

– Memory references made by the processor, for both instructions and data, tend to cluster together

+ Instruction loops, subroutines

+ Data arrays, tables

– Keep these clusters in high speed memory to reduce the average delay in accessing data

– Over time, the clusters being referenced will change -- memory management must deal with this

  • Performance of a two level memory

Example: Suppsose that the processor has access to two level of memory:

– Two-level memory system

– Level 1 access time of 1 us

– Level 2 access time of 10us

– Ave access time = H(1) + (1-H)(10) ns

where: H is a fraction of all memory access that are found in the faster memory (e.g cache)

Figure 9.3. Performance of a two level memory

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
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
hey
Giriraj
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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