REALLY LONG POST WARNING
Anyway, the latest big news right now is Apple's announcement to use Intel x86 processors in the new Macs. This is a big shift, as they used to be using processors made by IBM, and before that Motorola.
With all of these processors though, some people are bound to be confused. What is the difference between them? What would I want in a desktop? How about a laptop? Budget? Expensive? I'm so confused!
Relax. Today I'll cover the different major processors and what the differences are in mostly simple terms. This is a general overview though, so if you think I should cover it a bit more detailed, just let me know. The post is already long enough though. :P
Knowledge Rating: Probably not for new computer users. While I tried to explain things simplistically, a lot of new people will be lost. You are welcome to try though!
Processors are used for instructions by the computer - pretty much, everything you do on a computer is an instruction sent to the processor. While this is an incredibly simplistic definition, it works.
Processor speeds are measured in Hertz (Hz), or "cycle per second". Most times today processors are measured in Gigahertz (GHz) or "billion cycles per second". These speed values are often misleading, as just because something has a higher processor speed doesn't mean it is a better processor - in fact, today quite often that is not the case.
Another major feature of processors is the Front Side Bus (FSB) speed. The Front Side Bus speed is the speed that the processor receives instructions from the cache, basically. This is typically measured today in Megahertz (MHz) or "millions of cycles per second". While faster cache speeds in the same processor line is typically better, again the "faster is better" mentality is often misleading.
Number of bits. 32 bit vs. 64 bit is a debate that I'll leave to some other day in the future, but in general 64 bit processors are better, but software and drivers to use that capacity is required, which isn't really there yet as of this time in most areas, so this is something I'll just mention briefly.
The other major feature of processors is the amount of Level 2 (L2) Cache. The cache is where frequently used instructions or data are kept. Cache is many times faster than normal RAM, but many times more expensive as well, so typically only small amounts of it are kept. Cache is typically measured in Kilobytes (KB) or Megabytes (MB). There are 1024 Kilobytes in one Megabyte.
Other features (such as Level 1 Cache, pipeline length, SSE3 support, Hyperthreading support) are very numerous and sometimes important, but I'd like to keep this somewhat short.
There are a few major companies for PC chip manufacturers. Intel, AMD, and IBM are the three big players, so I'll cover those.
If you bought a computer from a prefab machine builder (Dell, HP/Compaq, et cetra) similar to this, chances are that you have an Intel brand processor of some type. There are a several major processor lines from Intel.
Celeron - Celerons are the low end desktop processors from Intel. While cheaper, they are far less efficient than other Intel processors of the same speed because of low amounts of cache and low FSB speeds. If you bought a cheap machine from a prefab maker, it is probably a Celeron. If you want to build a really cheap machine that won't be doing anything big and want an Intel processor, use this.
All Celerons are 32-bit to my knowledge.
Pentium 4 - Pentium 4s are the higher end desktop processors from Intel. If you paid more than 1000 USD for a machine from Dell, it is probably a P4. These easily outperform equivilent Celerons, but the newer Pentium 4s tend to have large power requirements and produce a lot of heat. Heat is bad for computers, by the way. If you see a Pentium 4 in a laptop, stay away. While they have a lot of power, they also drain a lot of power - battery power that is. Laptop makers wisened up more recently and P4 laptops aren't nearly as common as they used to be, but just be aware.
Most Pentium 4s are 32 bit, but the very latest ones are 64 bit.
Pentium 3 - While these processors are the older cousin of the Pentium 4 mentioned above, the only reason why I mention it is because this is what the current X-Box uses as a processor, basically.
Itanium - An older line of Intel processors for servers and high end workstations, these were some of the first 64-bit processors, and they failed. Badly. You'll see it mentioned around, but not even Microsoft is supporting these anymore.
Xeon - Current line of Intel processors for servers and high end workstations. This line is old. Really old. You aren't going to have one of these in your desktop machine at home, as they are meant for multiple processor computers like what most servers are.
Most are 32-bit, some of the newer ones are 64-bit.
Celeron M - The M stands for Mobile. Otherwise, pretty much everything said about the celeron applies here too. However, mobile processors use less power and produce less heat than desktop chips.
Pentium M - You may have heard the term Centrino mentioned with some laptops. Centrino basically is an Intel standard that includes wireless network access and a Pentium M processor. Pentium Ms are laptop processors that pack a lot of punch and use up VERY low levels of power (and produce far less heat). However, even though the M does stand for Mobile, Pentium M processors are being used in more than just laptops. The reason is that in some ways, the Pentium M is actually more powerful than a Pentium 4. While right now there are only a very few ways to get a Pentium M processor on a desktop, wait a year. That is because Apple has switched to using Intel processors for their Macs, and this is the processor they are using for both desktops and laptops. The processors also cost only slightly more than their desktop counterparts.
32-bit only. Great processor for laptops.
I'm not really an AMD fan, I'll admit it. It used to be that Intel chips didn't produce as much heat and, as a native Floridian, I care about heat quite a bit. Now, however, the tables have turned. If my next computer won't be with a Pentium M processor, it'll use an AMD chip.
Most machines custom built actually end up with AMD chips. That is because they are cheaper than their Intel counterparts and today they are also faster, more efficient, and cooler.
I don't have as much knowledge about them because of that, so this section will be a bit sparser.
Duron - Older processor, equivilent to the Intel Celeron. Pretty much the same things apply, but Durons aren't being made anymore. They've been replaced by Semprons. Very cheap processors.
Sempron - Newer low end processor. Faster and cheaper than Celerons in general. Otherwise, pretty much equivilent.
Athlon XP - 32-bit processor line equivilent to the Pentium 4. In general, they produce slightly more heat than a P4, and are slightly more efficient. The faster you go though, the less that these things are the case. No longer being made.
Athlon 64 - 64-bit processor line for desktops. Athlon 64s are cheaper, faster, use less power and produce less heat than a Pentium 4, in general. Downside is that you won't be using that all of that power unless you run a 64-bit version of Linux or Windows. It'll still work with normal versions of OSes, but you'll lose out on the advantages that 64-bit processors give you.
Athlon XP Mobile - Literally what it says, a mobile version of the Athlon XP. Compared to a Pentium M, they are slower, more power usage, hotter, and cheaper. 32-bit.
Athlon 64 Mobile - Everything I said about the Athlon XP Mobile can go here, except that this is 64-bit.
Opteron - Equivilent to the Xeon. I don't have much experience in this processor to be honest, but I know it is a 64-bit processor meant for servers and high end workstations.
They only really have two chip arcs that are well known for being in PCs. These chips are what are called non-x86 chips. This means that they aren't really compatable with x86 chips, which are pretty much all of the lines mentioned above save the server processors.
PowerPC - If you have a Mac that isn't really old, you have a PowerPC based processor. If you have a Gamecube, you have a PowerPC processor. If you are going to want an XBox 360 or Nintendo Revolution, you'll get a PowerPC processor. The processors are rarely used otherwise, and you probably won't be building a computer with one. In general, they are FAR more efficient than equivilent speed processors over in x86 land, but you won't be running Windows on these processors... Linux or Mac OSX typically.
Cell - The only people that have announced using this future processor is Sony. That would be for the Playstation 3. Supposed to be theoretically incredibly powerful, but it isn't in use yet.