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This document only covers IBM compatible PCs. Given that, we only describe systems that support AMD or Intel CPUs--though these steps are likely similar for other processor platforms.

You may find it strange that I start a builder's guide with software issues. Software is what drives the hardware on your PC. Without it you just have "a pile of electronics that gives off heat". If you are going to build a PC you need to know what Operating System (OS) you are going to use. This can be important because some operating systems don't have drivers for some hardware. This deficiency is steadily decreasing and is not the fault of the OS providers. Generally, it is the responsibility of the hardware manufacturer to write the drivers for the OS.

Hopefully, you know about Linux and the freedom it provides users. If not I encourage you to read the Linux section of this site for more information and learn why Linux is such a compelling alternative to other operating systems on the market.

If you are going to build a Linux computer (or "box", as they are called) you need to find out if a driver for that hardware has been written to work with Linux. More and more drivers are being written every day, there is still hardware out there which does not work quite right, or at all, with Linux. For the most part you shouldn't run into problems. The things you want to pay attention to primarily are Video/Sound cards or specialized cards. There are Linux driver sites you can search to find out if your existing hardware, or the hardware you want to buy has a Linux driver. CPU, Motherboard, Memory, etc... won't be affected.

If you decide to use Windows you should not have problems with which hardware to buy from an OS perspective because most PC hardware makers write drivers for Windows. This is due to Microsoft's virtual monopoly on the PC OS market.

There are several considerations when deciding which Central Processing Unit (CPU) to purchase.

When buying a CPU it is NOT all about the Megahertz (MHz). MHz is not a benchmark by which one can measure all CPUs. As you will see, there is more to be said about a chip than at how many MHz it runs.

The reason MHz is not a good yard stick for comparing chips is that different processors work differently. Some processors do more work than others each cycle. AMD CPUs, for example, execute more instructions (do more stuff) than Intel CPUs per cycle. If you were to compare the amount of work done by a 1.6GHz Pentium 4 (P4) in one clock cycle versus the amount of work done by an AMD Athlon XP running at 1.6GHz you would find that the AMD chip did more work than the Intel chip.

AMD chips are internally different, and work differently from those of Intel. That is why comparing the MHz of chips is not correct when considering which CPU will give you the best performance. It would be like comparing a Toyota running at 9000 RPM with a Mustang running 5600 RPM and selecting the Toyota just because it is running at a higher rate of RPM. There is more to be considered.

Other considerations are price and performance.

Price versus performance is an important factor to be weighed when considering which CPU to buy. I contend that AMD CPUs offer a better Price/Performance Ratio that Intel. AMD chips are less expensive than Intel chips and compete very well with Intel in terms of performace. AMD chips are also able to be overclocked directly without having to overclock your entire system--increasing system stability. The money you save on an AMD chip could be spent buying a better video card or faster Hard Disk Drive (HDD) or more memory, or better yet a faster CPU! These other devices have a significant role in system performance.

In addition to considering which manufacturer to buy from, you need to know what model of that CPU you want to buy. For example, you could buy a Celeron from Intel instead of a Pentium 4. Or you could buy a Duron from AMD instead of an Athlon Thunderbird or XP. So what is the difference? Well, there are a few differences, but from a CPU standpoint the cache is the biggest difference. The P4 has a much larger cache than the Celeron. Likewise the XP and Thunderbird (AMD) both have a much larger cache than the Duron. The Celeron and Duron were made to be inexpensive but good performance. Businesses often buy these processors for general office PCs because of their lower cost and bulk buying habits. If you want the best performance you should buy a P4 or an XP. If you are looking for good performance at the least possible price, then go with a Celeron or Duron. If you mainly check e-mail and surf the web, publish documents, etc... you can get away with not having a P4 or XP, but if you are a gamer or do video editing you should have a better processor because cache hits make a difference with these computationally heavy activities.

You should also take into account your existing hardware (compatibility and reason)

If you are looking to upgrade your system compatability is a very important. Likewise, if you are building a new system you must buy parts that are compatible.

You may want to upgrade your CPU.

If you have a Pentium 3 or Celeron CPU your motherboard has a 370 socket . If you are keeping the same motherboard you must buy a CPU that will fit in this socket. The only CPUs that fit in a 370 socket are P3s and Celerons. You will not be able to upgrade to a P4 without buying a new motherboard. The P4 uses a 478 socket.

If you own an AMD CPU (either a Duron or Athlon) you will be able to upgrade to the newer XP chip without problems. These three AMD chips use the 462 socket and will be compatible--from a socket standpoint--with your current motherboard. One thing to be aware of is that motherboards can only handle CPUs up to a certain speed. This is different for every motherboard. If you put too fast of a processor in your computer you will experience system instability and excessive heat, which can damage your electrical components.

You may have to buy new parts.

If you are buying a new motherboard then all you need to worry about is that the CPU will fit into the socket on the motherboard. I would advise you to buy a motherboard/CPU combo which will give you a motherboard and CPU. This way you can be assured that your CPU will fit in the motherboard.

If you don't want to buy a combo then, when you research motherboards, you need to make sure the motherboard is built for the CPU you intend to buy. This is generally easy to determine. Many motherboard manufacturers put a P4 in the model number of a motherboard if it was designed for the P4.

You must dissipate heat.

CPU heat is a topic worth spending a little time on. Today's CPUs run very hot. The need a Heatsink and Fan to cool them down. If you don't put one on, your CPU could melt and also melt your motherboard--depending on what kind of CPU you have. CPU manufacturers have approached this problem differently. Intel has made it so its CPUs will slow down considerably, thereby cooling the CPU. Of course, the CPU will be running very slowly and the system performance is tremendously reduced. AMD chips have no such heat control. They will burn up and melt if the HSF is off--and they will burn your motherboard next.

You should NEVER run your computer without a HSF on the CPU unless you want to see what burning a CPU and motherboard looks like and have to buy new parts. It is unusual that a HSF will might have fallen off during shipping or the knobs on the side of the socket that the HSF is attached to have broken. This is a rare/freak occurrence and you should not be too concerned. It is a good idea to look inside your computer when you receive it, if you do buy from someone rather than building it yourself, just to make sure everything is attached.

AMD's approach to heat is that it now requires motherboard manufacturers to put heat monitoring equipment on the motherboard (which is very inexpensive in terms of component cost) so that the motherboard can just shut down if the HSF falls off or stops working. I have this type of heat protection on one of my motherboards (Asus A7N266-E). This is not the ideal protection, but as I said it will probably never happen to you. It has never happened to me, or anyone I know. If this is a concern for you you need to either buy a motherboard that has thermal heat protection--there are different kinds, those that take a temperature reading via a thermal diode which are the kind you DON'T want, and those that use a protective circuit to determine the CPU temperature--or you can buy an Intel chip, which will cost more.

There's always debate over who's the fastest.

Some people want to get the fastest chip available and nothing less. The mentality that the fastest chip means the best system is incorrect. I can take a P4 system and make it run slower than a P2 if I misconfigure it. The point is that system performance depends on much more than just the CPU--though the CPU is quite important.

With that said, Intel makes the fastest chips for the PC. This is accurate in that its chips run at the highest MHz (analogous to RPMs) and that its fastest chip will outperform the fastest AMD chip. To see benchmarking figures go to this article at Tom's Hardware This site will give you a ton of information and I recommend looking at some of the hardware reviews before purchasing anything. Find something that you might want to buy and then look for an article about it on Tom's Hardware.

Desktop CPUs have recently changed from 32 bits to 64 bits.

The CPUs for the PC are 32-bit. That means that they process information in 32-bit chunks.

Both Intel and AMD are now coming out with 64-bit chips. These chips are better suited for a workstation or server (the thing that holds all the web pages that you are currently viewing--essentially a high quality computer running a high quality operating system like Linux) because you can use more than one of them together. The Intel P4 is meant to be the only CPU in your computer, as is the Athlon XP (uniprocessor systems). The Athlon MP (multiprocessor) was designed to work as one of two or more processors in a system. More processors can mean significantly more power depending on the hardware configuration and the applications you are running--more about this later.

Intel and AMD are taking different approaches to 64-bit processing. AMD is making a chip, the Opteron (or the ClawHammer which is kind of like a cheaper version meant for PCs), that will run in 32-bit mode with 64-bit extension ability so that it can function in a 64-bit environment and execute 64-bit instructions. Intel, on the other hand, is making the Itanium2 which is a better version of the Itanium they released earlier. Apparently the Itanium wasn't a huge success. Both the Itanium and the Opteron will use different Sockets than their predecessors so you won't have the option of upgrading just the CPU if you decide on these chips.

The main problem with switching to 64-bit is that most desktop software (at least software you paid for or stole/"shared" on the internet) was compiled and turned into binaries on a 32-bit machine. That means they will only run on a 32-bit machine. If you want them to work on a 64-bit machine you have to re-compile and re-link them on a 64-bit machine. In order to re-complie the software you must have access to the source code (the stuff the computer programmer made). This is not a problem if you use OpenSource software, which gives you the source code so you can re-compile it yourself. If it is closed source, proprietary software, however, what you really buy are the binaries--the already complied and linked code. Because you don't have access to the source code you have to wait until the software maker releases binaries and sells you the new 64-bit binaries--which they will be more than happy to do when there is enough demand. The main issues are making compilers and linkers or their equivalents for the different platforms.

There are 64-bit Linux ports available and there might be some for Windows. A port is like a version. There are versions (or ports) of Linux that require a 32-bit processor and there are versions (ports again) that require 64-bit (these are less common because Linux was made for the PC which uses 32-bit processors). Linux must be written for a specific type of processor because it uses some Assembler code (code is what makes up software and assembler code is referred to as "low-level" code meant to work with a particular piece of hardware). A small portion of the instructions (or code) in the Linux Kernel (the Kernel is like the heart of the operating system) are written in Assembler language for a 32-bit chip. This will have to be ported (make a new version) for the 64-bit chip. Confused yet?

Finally, the conclusion.

So, you need to know which CPU to buy. If you are upgrading make sure you buy one that fits into the socket on your motherboard. If you are upgrading or buying new, make sure you don't just go after more MHz. Look at the type of CPU and how big the cache is. Also, don't think that because this processor from this manufacturer runs at a lower MHz than this processor from this other manufacturer so the first one must be faster and better. This is not true so make sure you are familiar with who makes the CPUs you are looking at and the major differences between them.