This guide is partially in response to a current CPU purchasing guide. There were some good points made in 'AMD is better than Intel' and some not so good points, and some half-the-story points. I hope to clear that up and also to provide a more easily understood guide.
Your options when choosing a processor:
Processor Brand - AMD or Intel.
<Warning - fine detail, not necessary for average buyer>
As the previous guide stated AMD uses a shorter pipeline for its instructions to pass through. Yes this is a benefit IN SOME CIRCUMSTANCES. The full story is that a shorter pipeline means you are trying to achieve more per pipeline stage and so it becomes difficult to run at higher clock speeds. As such, AMD processors are only beginning to approach 3.0GHz. Intel, on the other hand, passed 3.0GHz a few years back. Now, for a simple set of instructions, say writing a fixed string to a serial port, there might be 500 instructions all executed in order. In this case, you would expect an Intel 3.0GHz to beat a AMD 2.0GHz, because the Intel can process 3 billion instructions per second (in simple terms) verses 2 billion by the AMD. However, in reality 500 instructions are nothing, a mere half a microsecond or less. What happens at the end is maybe a branch, a loop to try again, or even a task switch by your operating system. All these things could require a pipeline flush, and that means lag. Now processors these days are good at avoiding flush there pipelines (resetting each stage ready for a fresh stream of instructions), but they are not so good as to never have to do it.
Now, when a pipeline is flushed you get lag, because you are essentially throwing away all the half-done instructions and waiting for an instruction to pass through (which will take a clock cycle for every stage of the pipeline).. so you see a 10 stage pipeline, after a flush, will need to wait 10 cycles for new output, whereas a 20 stage will wait 20 cycles, comprende? that's the guts of the Intel vs AMD GHz myth.
In my opinion this can explain why some people call an AMD CPU faster and others, the Intel. My experience shows me that each is good at certain things; AMD seems to excel in games and interactive things, Intel win pretty convincingly in video/audio encoding/decoding and sometimes software compilation.
< OK everyone can tune back in now>
Processor Socket type - Socket A/462, 754, 939, 940, AM2, 478, LGA775 (probably missed some).
You need to match your socket type from CPU to Motherboard. Also check the website of your motherboard manufacturer to verify that the intended CPU is supported by the BIOS version you will get (avoid needing to upgrade the BIOS if possible).
No socket is necessarily better, although buying a newer socket processor means you are VERY likely to have support for all current CPUs, and also can leave you with a nice upgrade path if you find your CPU too slow a few years down the track; at least a side thought if not a priority.
Processor Speed - 'x' GHz. GHz doesn't mean as much as most people think, but obviously it means. a 2.8L Diesel 4WD might not actually drive faster than a 2.0L Mazda 323, but a 5.0L XR8 Ford should be better than a 4.0L GLi Ford.
You can kind of judge the AMD equivalent speed by its model number (eg. 3800+) but even that's not entirely accurate.
For simplicity most people won't know the difference between anything above 3.0 GHz Intel or above 3000+ AMD. you should buy purely on price above this point unless you actually have a particular function that you wish to have maximum speed for. In that case a recommend reading some hardware review sites; ie. www.techreport.com, www.anandtech.com, and from there discover which processor is better for your application.
Choosing a CPU - AMD or Intel
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22 August 2006
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