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PC World

How to install a faster processor

If your once-screaming computer seems to be showing you more of that hourglass cursor, perhaps it's time for a CPU transplant.

February 4, 1999
Web posted at: 4:59 p.m. EST (2159 GMT)

by Stan Miastkowski

(IDG) -- 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.

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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 CPU

1. Remove the old CPU

After you've done a complete backup, turn off your PC (but leave it plugged into a grounded outlet), remove the cover, and find the CPU. Usually, it's easy to locate, but you may have to unplug some cables or remove add-in cards to access it. If so, first note where everything is connected.

If your old CPU has a heat sink held on top by a spring clip, you may need a small screwdriver to remove the clip. If your CPU has a fan, disconnect the fan's power cable.

Very important: Before you remove the CPU, observe the corner that has a small diagonal cut indicating pin 1 (photo) and the corresponding pinhole 1 in the socket. Take careful note of the cut's position relative to the rest of the motherboard. You'll need to know where pin 1 goes when you put in the new CPU. (Hint: Use masking tape to mark the pin 1 location on the motherboard.)

The vast majority of computers made over the past three to five years have ZIF (Zero Insertion Force) CPU sockets. Touch a metal part of your PC's case to ground yourself, and with your other hand lift the lever that releases the CPU and carefully pull the chip straight out of the socket.

2. Install the new CPU

Remove it from its protective packaging and carefully insert it into the socket (photo). Don't force it; it should drop right in. Make absolutely sure that you have pin 1 of the CPU aligned with pinhole 1 (inset) of the socket. If it's not clearly marked on the new CPU, double-check the installation manual that accompanied the new chip. If you didn't mark pin 1 on the motherboard in step 1, check your system or motherboard manual. (If you don't plug in the CPU correctly, it's likely to be destroyed as soon as you turn on the power.)

Hold down the CPU firmly with your finger or thumb and carefully push down the ZIF lever to lock the CPU into the socket.

Connect the CPU fanto a free power connector from your PC's power supply. (Some CPU upgrades don't require separate power for the fan.)

3. Set the motherboard jumpers

To get the maximum performance out of your CPU upgrade, you must ensure that your motherboard's bus speed is set to 66 MHz and that its clock multiplier is set to the maximum value (usually 3.5X). Check the manual that came with your CPU upgrade for details on how to do this.

Some motherboards come with the required setting clearly marked, but most don't. Check the motherboard manual to make sure you're setting the right jumpers (photo). Setting jumpers incorrectly can result in a (temporarily) dead PC.

Some newer motherboards don't have jumpers. In this case, the PC should automatically detect the speed of the new processor and reset itself accordingly.

Some older motherboards (three to five years old) won't allow you to set the clock multiplier as high as the new CPU requires. In this situation the new CPU will still work, but not at its maximum speed.

Don't put the PC's cover back on until you're sure the system is working. Turn on your PC. If nothing happens, double-check that you've inserted the new chip correctly. If it still won't work, call the upgrade maker's tech support. If your PC does start up, run your applications to make sure everything is working correctly.

Installing a Pentium II-based PC

1. Remove the old Pentium II CPU

After doing a backup, turn off your PC (but leave it plugged into a grounded outlet) and remove the cover. If your existing PII cartridge has a built-in fan, remove its power connector from the motherboard, noting where it connects.

If your PII uses a large heat sink instead of a fan, the heat sink may be held to the motherboard by a pair of screws. Remove them carefully. Other PII-based PCs may use different schemes, such as a bar that holds down the PII assembly. If in doubt, check your system or motherboard manual.

A tiny lever on the top of each side of the PII cartridge (photo) unlocks it from the frame that holds it in. Press both levers in with your fingers until the levers click into their open positions. Then, grasping the CPU cartridge firmly, carefully rock it from side to side until it starts to loosen. Gently pull the cartridge upward from the frame.

2. Install the new Pentium II

Remove the new processor from its protective packaging and carefully slide the cartridge into the frame, making sure the fan is on the correct side. Press it firmly into its socket until the levers on each side click into the frame. Make sure the new CPU is seated securely. It shouldn't wobble.

Connect the fan power connector to the motherboard.

3. Set the speed

Most Pentium II motherboards have jumpers (photo) that must be set to match the speed of the new PII. If the appropriate jumper positions aren't marked clearly on the motherboard, check the manual that came with your PC for the charts and diagrams that indicate the correct positions.

Some PII motherboards don't have jumpers. In certain instances, you need to enter your PC's system setup utility (procedures vary) to alter the speed. In others, the manufacturer has provided a utility on floppy disk for CPU setup. Again, check your PC manual for the proper procedure.

Don't put the PC's cover back on until you're confident that everything is working properly. If your PC won't start, turn off the power switch, make sure the PII cartridge is firmly seated, and try again. If it still doesn't work, verify that the jumpers or other settings are correct. If all else fails, try Intel's tech support. (You'll find the information in the CPU's box.)

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