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Memory

Let’s say that you are fast asleep some night and begin dreaming. In your dream, you have a time machine and a few 500-MHz four-way superscalar processors. You turn the time machine back to 1981. Once you arrive back in time, you go out and purchase an IBM PC with an Intel 8088 microprocessor running at 4.77 MHz. For much of the rest of the night, you toss and turn as you try to adapt the 500-MHz processor to the Intel 8088 socket using a soldering iron and Swiss Army knife. Just before you wake up, the new computer finally works, and you turn it on to run the Linpack See [link] Chapter 15, Using Published Benchmarks, for details on the Linpack benchmark. benchmark and issue a press release. Would you expect this to turn out to be a dream or a nightmare? Chances are good that it would turn out to be a nightmare, just like the previous night where you went back to the Middle Ages and put a jet engine on a horse. (You have got to stop eating double pepperoni pizzas so late at night.)

Even if you can speed up the computational aspects of a processor infinitely fast, you still must load and store the data and instructions to and from a memory. Today’s processors continue to creep ever closer to infinitely fast processing. Memory performance is increasing at a much slower rate (it will take longer for memory to become infinitely fast). Many of the interesting problems in high performance computing use a large amount of memory. As computers are getting faster, the size of problems they tend to operate on also goes up. The trouble is that when you want to solve these problems at high speeds, you need a memory system that is large, yet at the same time fast—a big challenge. Possible approaches include the following:

  • Every memory system component can be made individually fast enough to respond to every memory access request.
  • Slow memory can be accessed in a round-robin fashion (hopefully) to give the effect of a faster memory system.
  • The memory system design can be made “wide” so that each transfer contains many bytes of information.
  • The system can be divided into faster and slower portions and arranged so that the fast portion is used more often than the slow one.

Again, economics are the dominant force in the computer business. A cheap, statistically optimized memory system will be a better seller than a prohibitively expensive, blazingly fast one, so the first choice is not much of a choice at all. But these choices, used in combination, can attain a good fraction of the performance you would get if every component were fast. Chances are very good that your high performance workstation incorporates several or all of them.

Once the memory system has been decided upon, there are things we can do in software to see that it is used efficiently. A compiler that has some knowledge of the way memory is arranged and the details of the caches can optimize their use to some extent. The other place for optimizations is in user applications, as we’ll see later in the book. A good pattern of memory access will work with, rather than against, the components of the system.

In this chapter we discuss how the pieces of a memory system work. We look at how patterns of data and instruction access factor into your overall runtime, especially as CPU speeds increase. We also talk a bit about the performance implications of running in a virtual memory environment.

Questions & Answers

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
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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.
Bharti
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
Daniel
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
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
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
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
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.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, High performance computing. OpenStax CNX. Aug 25, 2010 Download for free at http://cnx.org/content/col11136/1.5
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