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For many people, the main reason to replace their current computeris to get a faster processor.

After all, as the "brain" of your personal computer, won't afaster processor get work done in less time?

Not necessarily.

Not if the programs they use are more "disk intensive" than theyare "compute intensive."

Databases, for example, often get more boost from a faster harddrive than from quicker chips. And if you're hooked on 3-D graphicsfor professional design work or serious gaming, your need for speedmay be better served by a new graphics accelerator card. Or ifyou're looking for better performance when "multitasking" - runningseveral programs at once - then more memory is the key.

Faster processor helps

Still, a faster processor will probably help in each of thosecases and will be the critical item in calculating largespreadsheets, repaginating desktop publishing documents and manyother "compute intensive" tasks.

I'm always glad to get more megahertz, the measurement of how manymillions of software steps a processor makes each second. Earlypersonal computers only managed 1 to 5 MHz. Today's machines havereached 150 to nearly 500 MHz.

And newer processors sometimes bring benefits beyond more MHz.They might have more built-in "instructions."

For example, Intel's MMX instructions speed multimedia computingchores such as game graphics and photo editing. A Pentium with MMX,which is also built into all Pentium II chips, will be faster atmultimedia than a mere Pentium without the MMX, even at the samespeed. However, this is only true for programs that have beenrewritten to understand MMX.

New processor designs often have more on-chip "cache" - memorythat holds the most frequently needed information - and improved"pipelining" - the way instructions are lined up for their processingturns. Both of those design changes also affect speed. The PentiumII for Windows PCs has such improvements over the Pentium; the latestG3 PowerPC for Macintosh has them over the older 603 and 604 PowerPC.

But it isn't easy to know if a 300 MHz PowerPC G3 chip in a Mac isfaster or slower than a 400 MHz Pentium II chip in a PC, or when youought to consider a lower-cost Pentium "clone" such as the AMD K6chip, or even how much advantage a 266 MHz Pentium II has overIntel's own less-expensive 266MHz Celeron.

Check the benchmark

"Benchmark" results can help. These are programs that run aprocessor through timed, standardized operations. You might alreadyhave one at hand, such as the System Information tool in NortonUtilities. This tries to assign a single performance rating to yoursystem. That means it isn't just testing the processor, but othersystem elements such as the chip set - all the helper chips aroundthe processor. Some shareware benchmark programs you can downloadfrom the Internet, such as "CliBench," have a variety of tests,typically focused on mathematical operations.

But knowing how many times your PC can calculate pi in a minuteisn't as immediately practical as knowing whether a new processorwill speed up word-processing, World Wide Web surfing or photoediting. Various computer magazines - including PC, PC World,MacWorld - occasionally publish practical benchmark results, oftenwhen comparing several computers with identical speed processors.Peruse recent issues and you can sometimes find benchmarkedcomparisons of various Intel, Motorola and competing processorsattacking typical Word, Excel, Office and Photoshop tasks.

With all that in mind, if you're willing to spend the time andmoney installing a faster processor, what should you do next?

You could buy an entire new computer, for $1,000 or more. Thenyou get newer, faster everything, not just the processor.

The component route

You could spend a little less to buy new components. Start with a"motherboard" - about $150 to $200 - that holds the chipset and hasan empty socket for the processor. Then add some random accessmemory - say $100 for 32 megabytes. Finally, plug in a fastprocessor chip - from $200 for a Pentium II 266 MHz to $700 for aPentium II 400 MHz.

Then you'd probably want a fast new hard drive.... Wait, this isadding up to a lot of dollars and tech expertise - maybe pushing youback toward that new machine.

Yet there are cheaper and easier ways to get faster processing.

You could "overclock" your current processor. Your processorisn't actually set to a specific MHz. For example, "300 MHz" reallymeans "guaranteed to run reliably when paced by a 300 MHz clock andsurrounded by a chip set that can handle 300 MHz Pentium." Theprocessor will probably be fine running a little faster than itsguaranteed setting, and possibly a lot faster. It depends on whetherthe motherboard can handle the speed and on the internal quality ofthe particular processor chip. Even two chips from the samemanufacturing batch can have quality differences that mean one runsat 166 MHz and another can reach 233 MHz.

Free multiplier

On many computers, but rarely on portables, you can change theprocessor speed by opening up the computer case and fiddling with the"multiplier" settings.

It's free.

And it's a little dangerous. You'll certainly void the warranty,you could damage chips and connectors during the operation, and youcould overheat both your processor and surrounding components oncethe system is running faster. Overclocking can shorten yourcomputer's life, temporarily or permanently kill the processor, leadto more frequent crashes as you compute, or, worst of all, even leadto unreliable results - such as unnoticed wrong calculations.

That's a lot of risk for simply boosting from, say, 266 Mhz to 300MHz.

I wouldn't try it.

It's safer to actually buy a replacement or "upgrade" processor.You get a guaranteed faster chip and, if you don't already have them,other new design features such as the MMX instructions, or bettercache and pipelining.

The hard part is figuring out whether your PC can accommodate anupgraded processor.

Finding the right upgrade

You'll need to know details about the type of socket that holdsthe chip, the surrounding chipset and the underlying BIOS softwarethat boots your machine at start-up.

By far the easiest way to deal with this techno-speak is to visitthe World Wide Web sites of the companies mentioned below, or calltheir toll-free numbers, and see if they list your PC as upgradeable.

There are a few upgrades for 486 systems to either 486 chips orlow-level Pentiums; none I can find for 60 and 66 MHz Pentiums; and avariety of upgrade choices for Pentium 75 Mhz to 166 MHz models.

Even after finding the right upgrade, you'll still need some moretech expertise. You'll have to open the computer case, find andremove the older processor, plug in the new one, and close up, allwithout damaging anything along the way.

Or just get a new one

If you're not comfortable digging into computer guts, forget thewhole thing and just wait until you're ready to buy a new computer.

That's also my advice if you have a 486 PC, 60 to 75 MHz PentiumPC or an old PowerMac, say one that's four or more years old. Thereare so many other new elements in the latest PCs and Macs, and priceshave fallen, that a processor upgrade won't do enough.

If you have a more recent Mac, I'd look at new Mac pricesseriously before thinking processor upgrade. If you have a 166 MHzor 200 MHz or faster Pentium with MMX, you're too fast to get muchfrom processor upgrades. Consider adding RAM.

That leaves people with 75 MHZ to 150 MHz Pentiums. If youalready have 16 MB or more RAM in those, and especially if you usemultimedia programs that have been designed to use MMX instructions,you could get some good bang by spending processor upgrade bucks.