L2 Cache and Quad Processing??

[Beno]

Hi There Every1,

I'm doing my A+ cert right now and the talks of the Pentium Pro CPU have quad processing abilities which I think basically means that you can process 4 instructions simulatanesouly. How does this and dual processing work when instrcutions from the RAM to the CPU are given in 32 bit chinks pre clock cycle. Maybe Paleo Pete could have a go at this one for me!

One other question :-)

Why do we have L1 and L2 cache when for some CPU chips they are both internally within the chip. So why not just combine the 2 caches into one cache and call it L1??? And why is it that some L2 caches are etched within the silicon and some are outside of the CPU??

Any help would be kindly appreciated.

Cheers

Beno

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Have a nice day

[Ghost_Hacker]

And why is it that some L2 caches are etched within the silicon and some are outside of the CPU??

Because process technologies have gotten to the point where it is now possible to fit the L2 cache on the same die as the processor.In older processes the size and power consumption (read heat) of the processor and it's caches would be a detirment to increased clock speed.

Why do we have L1 and L2 cache when for some CPU chips they are both internally within the chip.So why not just combine the 2 caches into one cache and call it L1


The L1 cache is fast and small and the L2 cache is larger and a bit slower. Do you see the pattern? L1 cache,L2 cache, main memeory,hard drive....The further you get from the processor the slower and larger the "memory" device. This is called the memory hierarchy . In most systems the next device down the line holds a copy of all the information in the device before it. So in other words the L2 cache has a copy of all the data in the L1 cache. Main memory has a copy of all the information in the L2 cache and the hard drive has a copy of all the information in main memory. The reason I say "most systems" is because the Athlon's caches are not designed this way. Now here's the kicker.... the size of the L1 and L2 caches are consider the 'total of useful cache' for the system. In other words they're already consider one cache!!!!! So CPU designers will play around with the L1 and L2 cache's size,associative,bus and clock speeds to create the fastest 'total cache' for a given processor.


How does this and dual processing work when instrcutions from the RAM to the CPU are given in 32 bit chinks pre clock cycle.

Because the data bus does not feed the CPU. The data bus feeds the cache. As I pointed out before improvements to the L2 cache of the pro allows for 4 way systems.


Here's a good site for learning about the design of CPUs Aceshardware (http://www.aceshardware.com/Spades/list_articles.php?category=4) The forums on that site are visted by folks who design processors. If your brave and they feel like it. You might get them to explain it to you in more detail.


Good Luck http://www.PCGuide.com/ubb/smile.gif

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Comment heard from a Klingon programmer.

"Our users will know fear and cower before our software! Ship it! Ship it and let them flee like the dogs they are!"



[This message has been edited by Ghost_Hacker (edited 07-24-2001).]

[Ghost_Hacker]

Also ,just in case you haven't been there, here's a link to the PC guild chapter which explains SMP.


SMP (http://www.pcguide.com/ref/cpu/arch/ext_SMP.htm)


Here's a tidbit from the first page of that chapter.

"In addition, the Intel Pentium Pro or Pentium II are currently the best choices for multiprocessing because each chip has its own self-contained level 2 cache. In a system with more than one processor and level 2 cache on the motherboard, the processors must share the cache. Each new processor added to the system results in less cache per processor, which degrades performance. Each Pentium Pro or Pentium II however comes with its own level 2 cache, avoiding this problem and greatly improving performance, particularly on four-processor systems."

Hope this helps http://www.PCGuide.com/ubb/smile.gif

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Comment heard from a Klingon programmer.

"Our users will know fear and cower before our software! Ship it! Ship it and let them flee like the dogs they are!"



[This message has been edited by Ghost_Hacker (edited 07-24-2001).]

[sea69]

wow!

GH...

darned if that don't explain it all!

hehe

http://www.PCGuide.com/ubb/wink.gif



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homepage (http://www.seanweb1.homestead.com/3.html)


;)~