These Days, Chip Speed Isn’t Everything
When my wife and I were shopping for a car last year, the salesman opened the hood to point out the features of a high-performance engine. My wife, who’s something of a car buff, was actually interested. I glazed over it, preferring instead to concentrate on the important things such as the navigation system, six-CD changer and adjustable seats.
That’s the way it is with PC central processing units, or CPUs. Yes, they’re very important, but these days, any CPU that comes with a machine will get you where you want to go. Some might get you there a little faster under some circumstances--but many of us might never notice the difference.
Yet CPU speeds continue to be a selling point for PCs. The obsession to produce the world’s fastest and most powerful processor continues to dominate the engineering and marketing departments at both Intel and AMD--the two suppliers of CPUs for non-Apple PCs.
Intel last month shipped a 1.7-gigahertz version of its Pentium 4 processor. At the same time, it lowered prices on its entire line of chips. That gives Intel some bragging rights despite AMD’s argument that its 1.33-gigahertz Athlon processor is superior.
I’m not going to try to referee this electronic drag race, but I will try to put all the claims into perspective--or at least explain what the basic terms mean.
Intel makes three lines of central processing units for PCs. AMD has two. Intel’s Celeron processors are designed for lower-priced machines, followed by the Pentium III for mainstream systems and the Pentium 4 for the high end. AMD offers the low-cost Duron processor and the higher-end Athlon line.
Just to make things even more complicated, the chips come in different “clock speeds” measured in megahertz (MHz) or gigahertz (GHz). The clock speed is the speed at which the processor executes instructions. An 850-MHz processor, for example, operates at 850 million cycles per second. A gigahertz is a billion cycles per second.
If all things were equal, a higher clock speed would equate to a faster chip, but all things are not equal. There is also the issue of instructions per clock cycle, or IPC, which determines how many instructions are executed at each tick of the clock. Comparing clock speeds of different generations of CPUs is a little like comparing RPMs in a car. Just because a car engine spins faster doesn’t mean the car will win every race.
Another factor is the size of the cache--a bank of high-speed memory that serves as a buffer between the CPU and the main system memory. The size and speed of the cache help determine how quickly the CPU can get to the data it needs to process. The speed of the “bus,” which determines how fast data move between the CPU and the rest of the machine, also matters.
In case this isn’t confusing enough, there are lots of other factors including the basic design, or “architecture,” of the chip. Intel likes to boast about the NetBurst Micro-Architecture of its Pentium 4, which, among other things, takes advantage of “out-of-order speculative execution.” That translates to the chip’s ability to anticipate the data it needs to process, and if it “mispredicts,” it’s able to correct itself very quickly.
AMD, of course, makes equally compelling claims about its processors. The company points to its faster and larger cache memory and its “superscalar, fully pipelined, out-of-order, three-way floating point engine.” I’m not 100% sure what that is, but it has to do with the chip being able to do many things at the same time. The big question is whether all this actually matters. It doesn’t if all you do is surf the Web, write e-mail and use basic office applications such as Word and Excel. It matters a little bit if you work with photos and graphics and it matters a bit more if you edit video or audio files. It also starts to matter if you’re doing several highly computing-intensive things at once because a faster CPU has more power to share in a multi-tasking environment.
Remember there are other important considerations. Adding memory gives you a bigger performance boost per dollar than upgrading a CPU. And having a fast, high-capacity hard drive not only improves performance but makes life a lot easier.
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Technology reports by Lawrence J. Magid can be heard between 2 and 3 p.m. weekdays on the KNX-AM (1070) Technology Hour.
