Upgrade Guide

If your once-screaming computer seems to be showing you more of that hourglass cursor, perhaps it's time for a CPU transplant, one of the easiest and most beneficial do-it-yourself PC projects. But first consider whether a CPU Upgrade is worth the money and effort. Contrary to what you might think, doubling your computer's CPU speed won't necessarily double its performance. Other system bottlenecks, such as slow hard drives, leisurely graphics cards, and small amounts of RAM, aren't eliminated when you get a faster processor. A new CPU in an old system often yields no more than a 25 percent difference in performance, though your mileage may vary depending on the relative improvement in clock speed and the degree to which you upgrade other components. Our rule of thumb: A gain of less than, say, 100 MHz in processing speed generally doesn't repay the investment.

You also need to consider the cost of the upgrade. If the total upgrade (including more RAM, a new hard disk, and so on) costs more than 60 to 75 percent of a new system of comparable speed, you're probably better off donating your old system and purchasing an entirely new one. You can upgrade a 486-33 or 486-66 CPU to a 486-120 or 486-133 CPU for about $100, rev up the speed of a Pentium-75 or P-90 to 200 MHz for $100 to $150, and boost a Pentium-133 to 233 MHz for about $200.

Intel no longer manufactures its own OverDrive chips for standard Pentiums, but several companies do make plug-and-play upgrade kits. These producers include Evergreen , Kingston, and Trinity Works.

If you're not in a hurry, here's something to look forward to: Evergreen recently announced a radical new upgrade product--due out in the first quarter of this year--that puts the processor on a PCI add-in card. The company claims that this card will upgrade virtually any system (even a 486) by using Intel's Celeron and Advanced Micro Devices' K6-2 chips to achieve speeds beyond 400 MHz.

If your current PC has an early, "slower" Pentium II CPU, you can replace it with a faster version such as the Pentium II-333. But figure on paying a steep $450 to $475 for that chip. (Note: You can't upgrade an older PII PC to a 350-, 400-, or 450-MHz machine without installing a new motherboard.)

If your system uses a Pentium Pro chip, you can replace the CPU with an Intel OverDrive for Pentium II, boosting processing speed to 300 or 333 MHz. But at $549, this upgrade may not make economic sense for many systems.

Don't be tempted to purchase in the so-called "gray market" (through unauthorized resellers) an Intel, AMD, or Cyrix CPU. Even if you find a reliable source, these bare chips are difficult to install, and a wrong setting could destroy them instantly. Instead, opt for a complete plug-and-play upgrade package.

One final caveat: If your computer is more than about three years old, it may need a BIOS upgrade to handle a new CPU. Before you buy, check an upgrade chip maker's Web site for a list of compatible systems. Alternatively, some upgrade chips come with utilities that check your system for compatibility before you attempt the installation. All companies offer a money-back guarantee if the upgrade doesn't work.

• Upgrading a Pentium-Based PC
  
  
• Upgrading a Pentium II-Based PC