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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

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
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
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket 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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