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What makes a good processor?

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June 29, 2012 7:58:50 AM

I have built a few computers, now, and in my online shopping for the processor, I really only looked at the clock speed, and the L1, L2, and L3 caches.

I have a couple questions for you:

1) I was never sure what the caches meant, or what they do, I just realized that higher seemed to be better. Could you explain this in better detail to me?

2) What else should I be looking for in a processor? I have looked around in the past 10 minutes, and posts were saying things about the architecture of the processor. Could you also explain this in more detail, as well as other things I should be looking into.

Thank you very much for your time.

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June 29, 2012 8:12:07 AM

1)Cache is like ram for the cpu. it stores data.
2) Archetiure is well think of a building every building has a diffrent arch same as a cpu like the amd bulldozer claims its 8cores thats not really true its 2 moduels in one core
make sure you look up some benchmarks for the cpu, Rember just because a cpu has like 4.0ghz wont mean its fast its all about archteture
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June 29, 2012 8:15:13 AM

stanistheman said:
1)Cache is like ram for the cpu. it stores data.
2) Archetiure is well think of a building every building has a diffrent arch same as a cpu like the amd bulldozer claims its 8cores thats not really true its 2 moduels in one core
make sure you look up some benchmarks for the cpu, Rember just because a cpu has like 4.0ghz wont mean its fast its all about archteture


How do the different levels of cache work (L1, L2, L3), and why are they so small? (the highest I have seen is 8MB)
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June 29, 2012 8:22:08 AM

am10159 said:
How do the different levels of cache work (L1, L2, L3), and why are they so small? (the highest I have seen is 8MB)

Because it's breaking it down into levels the CPU can use. You know how the RAM only loads a small section of your HDD? Well, it's like that on a smaller scale. The amount of cache doesn't need to be huge, because it's all about what the CPU does with it.
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June 29, 2012 8:22:45 AM

am10159 said:
How do the different levels of cache work (L1, L2, L3), and why are they so small? (the highest I have seen is 8MB)

L1-cache is the fastest cache and it usually comes within the processor chip itself.
The L1 cache typically ranges in size from 8KB to 64KB and uses the high-speed SRAM (static RAM) instead of the slower and cheaper DRAM (dynamic RAM) used for main memory.
The Intel Celeron processor uses two separate 16KB L1 caches, one for the instructions and one for the data.

L2 cache comes between L1 and RAM(processor-L1-L2-RAM) and is bigger than the primary cache (typically 64KB to 4MB).

L3 cache is not found nowadays as its function is replaced by L2 cache. L3 caches are found on the motherboard rather than the processor. It is kept between RAM and L2 cache.

So if your system has L1,L2 and L3 cache data fetching will be L1->L2->L3->RAM
ie. If data is not there in L1 it will check L2 then L3 then RAM...
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June 29, 2012 8:29:53 AM

stanistheman said:
L1-cache is the fastest cache and it usually comes within the processor chip itself.
The L1 cache typically ranges in size from 8KB to 64KB and uses the high-speed SRAM (static RAM) instead of the slower and cheaper DRAM (dynamic RAM) used for main memory.
The Intel Celeron processor uses two separate 16KB L1 caches, one for the instructions and one for the data.

L2 cache comes between L1 and RAM(processor-L1-L2-RAM) and is bigger than the primary cache (typically 64KB to 4MB).

L3 cache is not found nowadays as its function is replaced by L2 cache. L3 caches are found on the motherboard rather than the processor. It is kept between RAM and L2 cache.

So if your system has L1,L2 and L3 cache data fetching will be L1->L2->L3->RAM
ie. If data is not there in L1 it will check L2 then L3 then RAM...


Thanks for the fast reply. What you said makes sense, other than the fact that most of the newer processors I see have L3 caches. Can you explain this? If it is slower, to have to go through the 3rd cache, why do they still have it on newer CPUs?
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June 29, 2012 8:33:42 AM

its to do with holding data before it is processed to put simlply, like a buffer.

"quote from here http://au.answers.yahoo.com/question/index?qid=20080312... "

L3 cache is not found nowadays as its function is replaced by L2 cache. L3 caches are found on the motherboard rather than the processor. It is kept between RAM and L2 cache.

So if your system has L1,L2 and L3 cache data fetching will be L1->L2->L3->RAM
ie. If data is not there in L1 it will check L2 then L3 then RAM..
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June 29, 2012 8:35:11 AM

L3 cache gives about a 10 to 15% performance gain.

L3 cache is like L2 cache its a little slower then the L2 but is larger in size.
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June 29, 2012 8:36:45 AM

To answer your other question am10159 i believe picking the right cpu for you will depend on what you want to do and how much you’re willing to spend.

Look at a selection of cpus you’re keen on and google benchmarks concerning those cpus. Best way really and for you to get the most out of your spending.
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June 29, 2012 8:39:48 AM

Yea boju is right. but let me tell you this. Intel cpus are faster. THERE is no slow core i7
wether its 1st gen or 3rd gen the core i7s are beasty line up. but if your on a budget get a core i5 2500k? or core i5 3570k the i5s are like i7s but dont come with hyperthreading. and well the core i7s come with bragging rights :D 
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June 29, 2012 8:40:01 AM

boju said:
its to do with holding data before it is processed to put simlply, like a buffer.


You answered my next question before I asked it :)  but I was wondering if you could go into more detail on exactly how it works. The explanation I got before said that the cache is like memory but it stores the location of data (I assume the data is in the RAM), not the actual data itself. Is this true? And is this also how it works on hard drives as well?

This seems pretty vague to me, so if you or another poster could expand on it, that would be great.
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June 29, 2012 8:41:54 AM

And whatever happened to i4 and i6? :p  I only see i3, i5, and i7 on the line-up
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June 29, 2012 8:42:51 AM

stanistheman said:
L3 cache gives about a 10 to 15% performance gain.

L3 cache is like L2 cache its a little slower then the L2 but is larger in size.


I've never really understood the purpose or process of L3 but forgive me if im wrong but searching L3 cache and its importance just now seems to be useless at this time.

Edit: this thread is going pretty quick so ignore what i say here lol
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June 29, 2012 8:58:05 AM

lol, seems that stan beat you to that one :p  copy and paste from there. Makes more sense now that I actually read the whole thing ;) 

But what about the caches that aren't doubled up like the intel one? If in that core, one part of the cache is used for instructions and the other for data, what about the processors which don't have the dual L1 Cache? (or L2, L3)
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Best solution

June 29, 2012 9:44:09 AM

Ever wondered why AMD is slower than Intel, even at higher clocks with more cores?
Its because Intel has a higher 'instruction per cycle' rate, meaning that whilst AMD's processors usually have a higher Clock frequency, they require more clock cycles to complete a task, Intel has made the CPU's have higher IPC's so that they can outperform other processors using less power, and less heat!
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June 29, 2012 10:46:48 AM

XavierTobin said:
Ever wondered why AMD is slower than Intel, even at higher clocks with more cores?
Its because Intel has a higher 'instruction per cycle' rate, meaning that whilst AMD's processors usually have a higher Clock frequency, they require more clock cycles to complete a task, Intel has made the CPU's have higher IPC's so that they can outperform other processors using less power, and less heat!


That definitely helps answer my question. Thanks a lot!

I am still fishing for details though.. If you can expand on this that would be great. I like learning new things :D  What I am looking for is how is the higher IPC;s achieved? Whats different between the AMD and intel processors (physically) that allows this?
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June 30, 2012 4:51:37 AM

am10159 said:
What makes a good processor?



Sugar and spice and everything nice.
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June 30, 2012 5:16:12 AM

Very helpful....
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July 7, 2012 12:08:46 AM

Best answer selected by am10159.
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