is cache memory used while copying operation ?

[rahulkothari]

u guys must have noticed if v increase the cache settings from BIOS, then the copying operation to and from floppy disk is carried out much faster ?

when i asked this question to a knowledgeable guy, he said cache mem doesnt come into the picture while copying (i.e. the processor itself isnt used while copying) only DMA is used and the data directly flows from the source to destination thru the DATA BUS. (i.e. while copyig from floppy disk to harddisk or vice-versa , data flows directly from databus whose eitehr ends are connected to f.d. and h.d.d. )

if this is so, then why does the copying operation become faster if v change the cache settings ?

i think, i m misinformed.

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An eye for an eye makes the whole world blind.
-Mahatma Gandhi

[YODA74]

try this http://ipdps.eece.unm.edu/1998/papers/247.pdf

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Death has come to our windows.

-- Jeremiah 9:21
(undoubtedly a Biblical reference to a Microsoft product!)

YODA74@carolina.rr.com

[YODA74]

opps

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Death has come to our windows.

-- Jeremiah 9:21
(undoubtedly a Biblical reference to a Microsoft product!)

YODA74@carolina.rr.com

[This message has been edited by YODA74 (edited 03-15-2002).]

[rahulkothari]

now ... that was not wat i wanted ? it was a total bumper. http://www.PCGuide.com/ubb/mad.gif
thx ... do reply if u even have a slightest idea of the topic. plz. coz the "knowledgeable guy" i mentioned in my post is none other than my college professor and i certainly think he is wrong.

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An eye for an eye makes the whole world blind.
-Mahatma Gandhi

[mjc]

What cache settings?

Is the floppy controller using DMA?

If the floppy controller is using DMA then what he said sounds correct, which is the purpose of DMA, frees up the processor, etc from handling mundane tasks by allowing two pieces of hardware to directly communicate with each other.

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mjc
Links list:Computer Links (http://www.dreamwater.org/tech/mjc/index.htm)

Celts are the men that heaven made mad, For all their battles are merry and their songs are all sad.

[YODA74]

Sorry thats not exatly what you wanted,here www.google.com (http://www.google.com)
Of course I guess thats why the Knowledgeable guy you mentioned has the cradentials of Professor? And your the student.

------------------
Death has come to our windows.

-- Jeremiah 9:21
(undoubtedly a Biblical reference to a Microsoft product!)

YODA74@carolina.rr.com

[rahulkothari]

thanks mjc for the reply. i searched and searched on www.google.com (http://www.google.com) (relation between DMA and cache, DMA cache copying etc) but didnt find any useful links. ok let me refine my question:-

Is data passed thru the cache memory while copying?

thx in advance.

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An eye for an eye makes the whole world blind.
-Mahatma Gandhi

[bassman]

As stated above, not if DMA is being used.
It really is that simple.

Often time, specific questions can come up during general discussion and the desire for an answer can override the learning process. Learn the pricipals of the technology being taught, then derive an informed theory form this.
Not trying to cut you off here, but it sounds like you do have more to learn before questioning the teacher http://www.PCGuide.com/ubb/wink.gif

Good luck

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A real Christian is one who can give his pet parrot to the town gossip.
Frank's Place (http://dreamwater.net/tech/frankscomp/)

[rahulkothari]

Originally posted by bassman:
As stated above, not if DMA is being used.


thx bassman. probably u r right. i have to learn more. http://www.PCGuide.com/ubb/rolleyes.gif
... but still then ... one thing is for sure


cache memory is not used while copying operation (to and from floppy)


... then y does the copying operation become faster when v increase the cache settings from BIOS (i.e. if v increase the settings of L2 cache from say 256kb to 512kb in case of Pentium3 500mhz)?

plz answer it as v dont have the topics in this detail(i just wanna know) and hence its not possible for me at this stage to study hundreds of books, coz my exam is in april. http://www.PCGuide.com/ubb/frown.gif

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An eye for an eye makes the whole world blind.
-Mahatma Gandhi

[iisbob]

OK, this is a common misconception i've seen about how DMA and CPU's work.

The cpu is not really " skipped " when DMA comes into play, it justs acts as a traffic cop, when an item, like the floppy, supports dma-it doesn't just ignore the CPU, it just gets re-routed using the dma chipset.

Think of it like this; w/out dma cmd to copy goes from media,cpu,media-w/dma enabled the cpu recognizes that there is a dedicatd bus to transfer data so it doesn't process the data, instead it passes the instructions on to the dma chipset on the motherboard, basicly it " hands off " the process, but it still keeps an " eye " on it.

The reason you see an increase in performance when you increase the cache is now the CPU has more " prefetch " storage space alloted, so it can process more instructions quicker.

simple enough http://www.PCGuide.com/ubb/smile.gif

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iisbob

"It is by the fortune of God that, in this country, we have three benefits: freedom of speech, freedom of thought, and the wisdom never to use either."
-Mark Twain { Samuel Clemen's }


[This message has been edited by iisbob (edited 03-18-2002).]

[rahulkothari]

ah ha. that was simple. thx.

actually when i said 256kb-512kb i meant writethru and writeback. sorry for giving the wrong info. actually i checked my bios months back and hence didnt remember the settings. sorry , it wont happen next time. http://www.PCGuide.com/ubb/tongue.gif



The reason you see an increase in performance when you increase the cache is now the CPU has more " prefetch " storage space alloted, so it can process more instructions quicker.


now did u mean the copying performance(COPYING SPEED) or the regular performance ?
coz acc to yor ans, cpu just keeps an "eye" over the operations, that is the data doesnt pass from the cpu and the cache when dma is used.

also, can i find out whether dma is used for "copying operations" in my system ?

if in my sys, dma is not used, then i got the solution.

w/out dma cmd to copy goes from media,cpu,media


and if its used, i m still confused.

thx to all those replied and ... will reply (hopefully)

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An eye for an eye makes the whole world blind.
-Mahatma Gandhi

[This message has been edited by rahulkothari (edited 03-18-2002).]

[Ghost_Hacker]

now did u mean the copying performance(COPYING SPEED) or the regular performance


The thing to remember is that the CPU controls the floppy drive , in other words the "commands" that operate the floppy come from the CPU. When you increase cache you increase the speed of the CPU's command execution not the speed of the actual data transfer. The data transfer is taken care of by the floppy disk controller and the DMA controller.

All computers made for some time now come with DMA controllers with DMA 2 being assigned to disk drives.


You might find this link interesting:
http://www.infran.ru/TechInfo/BSD/handbook257.html




[This message has been edited by Ghost_Hacker (edited 03-18-2002).]