CPU help. Can some one explain them? - Techist - Tech Forum

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Old 07-23-2008, 02:54 AM   #1 (permalink)
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Default CPU help. Can some one explain them?

I want to begin plans on building a computer because the computer I have now is ridiculously slow. I figured I'd start with finding the right price & performance CPU, then find a mother board that supports it. However, this is beginning to look impossible.

I have no idea how good a processor is. I wouldn't know the difference between a week processor and a strong processor. I remember once upon a time you generally went by its Operating Frequency: the higher the number the faster and better the processor. But so much has changed (or maybe back in the day I was very illiterate as to how CPU's functioned).

I see a lot of functions and features that I just don't understand, such as:
1. Socket Type
I imagine the only differences are which motherboards these things will work with, and it has nothing to do with performance.

2. How many cores they have (Single Core, Duel Core, Quad Core)
It would seem the more cores the better. But the question is "how much better". Is a 1GHz duel core CPU as fast as a single core 2GHz CPU, and a 1GHz quad core run as fast as 4GHz single core?

3. Front Side Bus vs. Hyper Transport.
Just how important are the speeds of these two things and what is the difference between these two things (if any). I see some CPU specs listing the speed of its FSB and others listing the speed of its Hyper Transport, but I haven't seen one listing both so I am assuming these are two different ways of skinning the same cat and the number is the only real important part.

4. 64 bit vs. 32 bit
All the CPU's I see claim they "support" 64bit. I guess that means if the Operation System I am running doesn't support 64bit than the CPU might as well be a 32bit. But if I were to get a 64bit operation system, what does it really mean? Does this mean a '64bit 1GHz processor' has twice the speed of a '32bit 1GHZ processor' in a 64bit environment?

5. Chip architecture (45nm Harpertown, 65nm Brisbane, 65nm Allendale, 90nm Italy, and so on).
What does any of that stuff mean? Should I just ignore it? Should I just care about the number, or does the name after the number really count? Is any of it really going to affect processor performance on a significant level?

6. Caches (L1, L2, L3)
First, just how important is the cache size? And is a CPU with 3 caches better than one with 2 caches? Can someone show me the math or give me an idea of what the cache is all about.

I read an article about L2 Cache on Wikipedia. After reading it, I wanted to blow my brains out, that's how confusing all that is. It talked about the processor's cache being faster than memory, but then goes on about data retrieval with hits and misses and how it's all about Replacement Policy. And I come away with the impression that the Replacement Policy is more important than the cache size. Or am I blowing that out of proportion?

Is there any mathematical formula to figure out which processor really runs fast/better, sort of like an ohms law or something?

Anyhow, I sure could use some answers.
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Old 07-23-2008, 03:14 AM   #2 (permalink)
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Default Re: CPU help. Can some one explain them?

I'll see if I can explain a few of those things for you.

ARCHITECTURE
The number part of the chip architecture (e.g. 45nm) is how big in nanometers the transistors are on the cpu. Obviously, if they are smaller, more can fit. Meaning faster cpu.
The name is just that, a name. Code-name given by Intel to differentiate between the different processor types.

CACHE.
It is VERY important, and is basically what the cpu uses to quickly store and retrieve some of the data it processes. The more cache a processor has, the faster it will be.

FSB
the Front Side Bus carries information between the cpu and the northbridge on your motherboard. The northbridge handles a lot of important communication between your RAM, CPU, etc. So the faster your fsb is the better.

SOCKET TYPE
You got the right idea with the socket type. They change after a while, as better ideas get processed, but they only really matter to you in terms of getting a mothereboard which has the correct socket for your cpu

lol, all I've got time for atm, hope that clears up a few things for you.
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Old 07-23-2008, 02:37 PM   #3 (permalink)
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Default Re: CPU help. Can some one explain them?

CACHE, CONT.
The analogy I heard to help keep cache straight is thinking about a library. The harddrive is the stacks. Each time you want a book, the librarian had to go to the stacks to grab it. But if the librarian kept the top 20 most commonly checked out books at the front desk, those operations would be faster. Think of the front desk as the cache. The larger the front desk (cache), the more books (operations) can be stored for quick retrieval. L1, L2, and L3 are levels of cache, and would be analogous to, say, front desk, desk behind front desk, and desk behind desk behind front desk - three levels before you have to go to the stacks.

64 BIT vs 32 BIT
64-bit and 32-bit are based on instructions; the only think I know about it is that 32-bit operating systems can only use a little less than 4GB or RAM, because it simply does not have a big enough address space to specify anything larger than 4GB. 64-bit on the other hand can go beyond 8GB ram. My guess is that a CPU needs to be compatible with the 64-bit architecture in order to utilize a 64-bit operating system and thus larger amounts of RAM.

HOW MANY CORES THEY HAVE
For your single core vs. dual core, check out this link:
Common Noob Myths - Computer Forums
It answers your question and potentially others you might have in the back of your mind. I know I've made several of these assumptions/mistakes.
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Old 07-24-2008, 10:54 AM   #4 (permalink)
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Default Re: CPU help. Can some one explain them?

Just to expand on what others have already posted:

1. Socket Type - This is exactly what the name infers, just the connection type. Generally speaking you should find the CPU you want, then find a motherboard with a matching socket type. A cpu of one socket type will not fit in a motherboard of a different socket type. These two MUST MATCH.

2. How many cores they have (Single Core, Duel Core, Quad Core)
Cores is how many cpu's they fit on a sigle dye (chip). Cpu's are so small today (45 nanometers) that they can fit multiple cpu's on one chip. This means that you can do more computations with the same chip (b/c on that chip there are more cpu's). So when you have a dual core you actually have two processors in the same chip, and with quad you have four processors on the same chip. This is not to be confused with multiple processor computers like servers, which actually physically have multiple cpu chips on the same board. Mathmatically speaking a 1 ghz dual core chip will MORE THAN double the output of a 1 ghz single core chip. I'm not a math major but the reason is because of efficiency. Two processors on the same chip (so they communicate extremely fast b/c they are in the same dye) will compute more than twice as fast as one. So a 1 ghz double core processor will more than double the output of a 1 ghz single core. I should note that your OS/software must be able to multithread (send more than one process to the cpu) in order to take advantage of multiple cores.

3. Front Side Bus vs. Hyper Transport.
I think Soul explained this one well. The faster the better in general, because it is the speed to which the processor/ram/gpu are communicating.

4. 64 bit vs. 32 bit
This one confuses a lot of people. Yes there is the instant advantage of being able to hold more than 4 gig of ram on a system running a 64 bit OS. But the advantages DO NOT stop there. Overall your system will perform much faster (almost double) running at 64 bit. So identical systems, one running 32 and the other running 64 bit, compared the 64 bit would almost run twice as fast (assuming the OS/Software can run 64 bit). Think of it this way, if you had 128 bits of data to move from one room to the other. And you had a bucket to carry them in, with a 32bit bucket you would have to move back and forth 4 times in order to move all of that data. Now with 64 bits your bucket is twice as big, allowing you to complete the task in 2 trips. So the advantages are not just in RAM capacity, your software, os, and mb will be able to transfer data (commands) at a much faster rate, resulting in better overall performance.

5. Chip architecture (45nm Harpertown, 65nm Brisbane, 65nm Allendale, 90nm Italy, and so on).
45 nano meters is the size. These are just the sizes of the processors, and the name is just a code name for the processor. The name really means nothing, just a way to tell different processors apart instead of saying "ya i have a 45nm Harpertown with 1 mb L2 cache and 512 kb L1 cache" you can just say you have an Intel Harpertown.

6. Caches (L1, L2, L3)
This is where data (commands) are stored ON THE CHIP ITSELF. So the data can be acccess at incredible speeds. So the CPU doesn't have to look off the chip for the code to say move the mouse around. With larger caches (in generally the larger the better) the cpu can store more commands on the cpu ship itself, meaning that the process of moving your mouse, opening a program, etc (depending on what it stores in the cache) it can just grab the code from the cache, instead of moving accross the bus speed of your system to get the code from RAM.

Replacement policy is important, but cache will definately help the speed of your processing. It also depends on the manufacturer (i know more variables). Intel chips use a north bridge to communicate between ram and the gpu, but amd chips have a pipeline straight to the ram. So in the gaming community your commands (hard core processing like games) are not stored in the cache, so cache really doesn't effect gaming performance much. Which is why amd is more popular, because the cpu can communicate with the ram directly.

No i don't believe there is a magical formula, there are WAY TOO MANY variables involved. Really i would suggest reviewing what you will use the computer for, then build accordingly. Another thing to consider is power consumption, the cpu's today are actually trying to use less energy then before, so keep that in mind too.
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Old 07-24-2008, 11:56 AM   #5 (permalink)
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Default Re: CPU help. Can some one explain them?

Just buy a q6600 or an e8400 and a good LGA775 motherboard.
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Old 07-24-2008, 08:41 PM   #6 (permalink)
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Default Re: CPU help. Can some one explain them?

lol, i say...lol.
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Old 07-24-2008, 09:37 PM   #7 (permalink)
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Default Re: CPU help. Can some one explain them?

Well I think you people very much for your answers. At least now I have a slightly better understanding of CPU's. I still have some studying on the subject to do but at least have enough understanding to know where to begin.

and here's a question for Lexluethar
Quote:
Two processors on the same chip (so they communicate extremely fast b/c they are in the same dye) will compute more than twice as fast as one. So a 1 ghz double core processor will more than double the output of a 1 ghz single core. I should note that your OS/software must be able to multithread (send more than one process to the cpu) in order to take advantage of multiple cores.
Which Operation Systems support multithreading?
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Old 07-24-2008, 10:56 PM   #8 (permalink)
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Default Re: CPU help. Can some one explain them?

pretty much anything from the past 8 years supports multithreading.
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Old 07-25-2008, 08:49 AM   #9 (permalink)
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Default Re: CPU help. Can some one explain them?

Most support it, in fact i don't know what doesn't support it. It was just somethign worth noting because your OS won't automatically use multiple processors, it has to support multithreading. The comment was more for you to understand - like dawn said they've had multithreading since the pentium 4 single cores.
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