Although mainstream slotted processors are now obsolescent, they remain in limited distribution. A faster slotted processor may be a worthwhile upgrade for an older system. Installing a faster slotted processor can greatly improve system performance and extend the useful life of an otherwise obsolescent system.

For example, until late 2001 our Internet gateway system was an older Celeron. We'd been having some problems with it locking up, which we suspected were caused by the commodity memory installed in it or by the undersized power supply. One day, after three lockups in as many hours, Robert (who is a procrastinator) finally decided to do something about it. We tore down that system and replaced the power supply with an Antec unit and the 64 MB of generic memory with a 128 MB Crucial stick.

While we had the case open for a cleaning and general upgrading, we noticed that the system still had its original Celeron/333 installed, so we decided to replace it with a Pentium II/450 that we'd pulled from another system. The faster clock speed and larger L2 cache of the Pentium II yield performance nearly twice that of the original processor, which takes that system from marginal to more than sufficient for the gateway and mail server tasks to which it is devoted. For a cost of less than $100 (even if we'd had to buy the processor), we now have a reliable Internet gateway system that we expect to continue using for several years to come.

Installing a slotted processor is in some ways easier than installing a socketed processor and in some ways harder. Intel manufactures processors for two similar but incompatible slots. The 242-pin connector, formerly called Slot 1, accepts slotted Celeron, Pentium II, and Pentium III processors. The 330-pin connector, formerly called Slot 2, accepts Pentium II/III Xeon-class processors. These various processors come in different physical packaging (SEC, SEC2, SEPP, etc.), each of which uses a different retention mechanism. For example, an SEC Pentium II and an SEPP Celeron both fit the same Slot 1, but use different and incompatible retention mechanisms.

To further complicate matters, Intel ships the same processor in different variants. For example, the retail-boxed version of the Pentium II processor comes with an attached fan, while the OEM version of that processor does not. If you purchase an OEM processor with an attached fan, that package may or may not fit the standard retention mechanism (although it usually does fit). So, the first rule is to make sure that the retention mechanism accepts the processor. If you purchase a cooling device that does not fit the standard retention mechanism, it should be supplied with a mechanism that fits it. Thankfully, all retention mechanisms mount to the standard set of holes in Slot 1 motherboards. Fortunately, AMD Slot A processors are a much simpler matter. All of them use the same physical mounting mechanism, and all Slot A motherboards can accept any Slot A processor. To install a Slot 1 Intel Celeron/Pentium II/Pentium III or a Slot A AMD Athlon processor, take the following steps:

• 1. When installing a new processor in an older system, determine if a BIOS update is available because the processor may require a later BIOS to support its new features. For example, the Intel SE440BX2-V motherboard accepts various Slot 1 processors, including some Pentium IIIs. But you must upgrade the BIOS to take advantage of the new Pentium III SIMD instructions. Installing the Pentium III without upgrading the BIOS simply makes the Pentium III run like a faster Pentium II. If a new BIOS is available, download it and update your PC.

• 2. Move the PC or motherboard to a well-lit work area, preferably one with all-around access. Collect all of the tools, software, manuals, and upgrade components you need. Read through the processor documentation before proceeding.

• 3. To install a processor in a new motherboard, ground yourself, remove the motherboard from its packaging, and place it flat on its accompanying antistatic bag. If you are installing a new processor in an existing PC that uses a compatible retention mechanism, you can probably do so without removing the motherboard, although you may have to reroute or disconnect cables to gain unobstructed access to the slot. If the retention mechanism needs to be replaced—e.g., when upgrading a Celeron system to a Pentium III—you may or may not have to remove the system board to replace the retention mechanism.

• 4. If it is not already installed, install the retention mechanism by following the instructions supplied with it or with the motherboard. Standard retention mechanisms are notched at one end to match the notch in the Slot 1 connector on the motherboard. Align the retention mechanism and seat the four posts into the matching holes on the motherboard. Press down firmly until the retention mechanism seats. Each post has a sliding internal pin topped by a flat, circular piece of white plastic. Forcing that pin down into the post expands the bottom of the post on the far side of the motherboard, securing the post to the motherboard. Press down each of the pins until it snaps into place. Some newer Slot 1 motherboards come with the retention mechanism already installed, but with the vertical supports folded flat. If your motherboard is like this, lift the vertical supports until they snap into place.

• 5. If the cooling device is not already installed on the processor, install it now. Some processor packages also contain a supplementary support mechanism designed to secure the processor against the additional weight and vibration of the cooling fan. If your package contains such a supplemental support, install it on the processor according to the instructions provided with it.

• 6. Refer to the processor documentation to determine the proper settings for bus speed and CPU multiplier. Refer to the motherboard manual or manufacturer web site to locate configuration jumpers and to determine the jumper settings that match those required by the new processor. Some boards have separate jumpers for FSB speed and CPU multiplier, others have jumpers for CPU speed only (which implicitly sets both FSB speed and CPU multiplier), and still others use "jumperless setup" which sets FSB and CPU multiplier options in CMOS Setup. Slot 1 processors do not require voltages to be set manually. All current Slot 1 processors use 3.3 volts for external I/O. Klamath-based processors use 2.8 volts internally, and Deschutes-based processors use 2.0 volts. Voltage setting is handled completely automatically via the Voltage ID (VID) pins on the processor itself.

• 7. Once you have made necessary jumper changes, if any, install the processor, first removing the existing processor if necessary. Note that the card-edge connector on the processor has a key notch, as does the slot. Slide the processor into the support bracket, making sure that the key is oriented properly.

• 8. Using both thumbs, press down firmly on the processor until it seats fully. This may require applying significant pressure, but you should feel and hear the processor seat. Most support brackets have locking tabs at the top that will snap into place to secure the processor once it is fully seated.

• 9. If the fan power lead is designed to connect to a motherboard power header, connect it now. If the fan power lead instead is designed to connect to a power supply power connector, you'll make that connection after the motherboard is installed in the case.