Factors Affecting CPU Performance

There are several factors that affect processor performance. Understanding these factors will help you make the proper choices when designing your homebuilt computer.

The most important factors affecting processor performance are:

Instruction Set

This is the processor's built-in code that tells it how to execute its duties.

You really have no control over the instruction set. It is built-in to the CPU. But together with processor architecture, it does affect performance across a given line of CPU's; and so it is mentioned here just for the sake of accuracy.

Clock Speed

The clock speed is stated in megahertz (MHz) or gigahertz (GHz), and is a measure of how many instructions the processor can execute in one second.

All else being equal, processors with faster clock speeds process data faster than those with slower clock speeds. It's also the first number you will see in advertisements for CPU's. But don't select a CPU based on clock speed alone. It's only one of the factors (albeit an important one) that determines how well a CPU will perform in real-world situations.

Bandwidth

Measured in bits, the bandwidth determines how much information the processor can process in one instruction. If you were to compare data flow to the flow of traffic on a highway, then clock speed would be the speed limit, and bandwidth would be the number of lanes on the highway.

Most existing desktop computer systems today run on 32-bit processors, but more and more new PC's are coming equipped with 64-bit chips. It's expected that all new operating system releases (such as Microsoft's upcoming Windows Vista) will either require or be optimzed for 64-bit processors, so it makes sense to design your new computer around a 64-bit CPU, like the Athlon 64 3500+.

Front Side Bus (FSB) Speed

The FSB is the interface between the processor and the system memory. As such, the FSB speed limits the rate at which data can get to the CPU, which in turn limits the rate at which the CPU can process that data. The CPU's FSB speed determines the maximum speed at which it can transfer data to the rest of the system.

Other factors affecting data transfer rates include the system clock speed, the motherboard chipset, and the RAM speed.

On-Board Level-2 (L2) Cache

The on-board (or "on-die") cache is a little bit of high-performance RAM built directly into the processor. It enables the CPU to access repeatedly used data directly from its own on-board memory, rather than repeatedly requesting it from the system RAM. L2 Cache is very critical to applications such as games, video editing, and 3-D applications such as CAD/CAM programs. It's less important for activities such as web surfing, email, and word processing.

Most low-cost CPU's have as little as 128K of L2 cache. Higher-end CPU's have up to 1 MB.

Heat and Heat Dissipation

When processors run too hot, they can start doing funky things like cause errors, lock, freeze, or even burn up. Installing an inadequate cooling system can cause your homebuilt computer project to go sour in a big (and possibly expensive) way. So don't skimp on the cooling.

 

Confuzled? Don't worry. The next page will simplify things a bit.

Getting Started