AMD vs. Intel Architecture Discussion

Posted by in January 23rd, 2005

Both AMD and Intel have their devoted fans and sometimes their bias can lead to bad advice on which CPU to buy. Here, ZeGermans sets aside bias and helps debunk the myths of the CPU wars.

Every time the debate between AMD and Intel CPUs is brought up, the same arguments are offered: "AMD rocks for games! Intel is good at everything else! If you only game, get an AMD!” Now, this statement isn’t entirely true. This article will examine where this blanket statement is right and where it is wrong about AMD’s and Intel’s advantages, and will also explain how their respective chip architectures lead to these advantages and disadvantages.

The first problem with the above statements is that it tries to generalize for all AMD chips. However, it is only in the past year, with the release of the Athlon64, that AMD has pulled ahead of Intel in gaming performance from a price vs. performance standpoint. Until this point, Intel’s Pentium 4 C’s (the ones with 800FSB) crushed any of the older Athlon XPs on the market. For the purposes of this article we will only examine Athlon64 chips and ignore Athlon XPs, as the architecture for the latter chip is dead and gone.

The next problem with the statement is that it doesn’t really give AMD enough credit. Most well regarded benchmarking sites such as www.anandtech.com and www.xbitlabs.com test many properties besides gaming on their CPUs. The areas of analysis include business use, office use, content creation, 3D content creation, multitasking, photo editing, video editing, video/audio encoding, gaming, and workstation performance. From this list, AMD ranks above Intel in the categories of business, content creation, photo editing, gaming, and non-3D workstation performance. As this extensive list shows, AMD processors are good for many more tasks than just for gaming as our statement in question would suggest.

With this true performance ranking for AMD established, we must ask why it is that AMD excels at tasks that are generally hard to calculate, such as workstation performance, business applications, and gaming, while Intel’s strengths lie in the more rudimentary calculations, such as encoding and video editing. The answer lies in the different architectures of the two processors, and the main difference in this architecture has to do with the pipeline of the chips. The pipeline is the path that every calculation takes down the CPU; depending on what task the CPU is doing, it will use different branches of this pipeline. Think of this as an assembly line: the longer the assembly line, the quicker and more efficiently goods will be produced. Intel’s pipelines are much longer than AMD’s, which is why Intel has an advantage in various tasks.

Now, with the pipeline in mind, you are probably asking yourself why Intel does not beat AMD in all tests. This is because of the branch predictor: as a signal goes down the pipeline, the branch predictor, as the name would indicate, predicts the branches that the signal should go down. The problem is that the predictor is not always correct, and if it sends a signal down the wrong branch it will have to start over from the very beginning. Branch predictors miss their targets much more with complex calculations, such as gaming. In this type of application, a chip with a shorter pipeline will have an advantage because if the branch predictor were to be incorrect, the signal will not have as far to go again after it restarts.

Assuming that everything goes down the pipeline without a problem, Intel chips have a clear advantage in every possible application. AMD comes out on top in tasks such as gaming because, simply, things hardly ever go down a CPU’s pipeline perfectly.

I would hope that the next time you find yourself in an AMD/Intel fanboy war, you’ll now have enough knowledge to inform both sides of how they are wrong, and in the long run help to make my life in the Computer Help forum a little easier.

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