Pentium Pro Through Pentium III

After the Pentium, Intel released a series of upgraded versions of the Pentium CPU, known as the Pentium Pro, Pentium II, Pentium III, and Celeron. These CPU families differ from the Pentium in several ways, including

• L2 cache on the CPU package L2 cache is a fast type of RAM that, on Pentium designs, resides on the motherboard. These CPUs place it on the CPU's package, although it's not part of the same microchip wafer as the CPU proper. This placement speeds up system performance because the cache can run at a faster speed than it could when placed on the motherboard. Early Celeron CPUs, however, lacked the L2 cache.

• 36-bit addressing These CPUs can access 236 bytes, or 64GB, of memory, as opposed to the 4GB limit of the Pentium line.

• Improved speed Although not as radical as the speed improvements in some early generation changes, these CPUs are generally faster than their predecessors when set at the same clock rates. The Pentium Pro is actually slower than the Pentium when running 16-bit code, but faster when running 32-bit code. (Linux uses 32-bit code exclusively, except when running emulators like DOSEMU.)

Part I

• Improved clock speeds These CPUs can run at faster clock speeds than their predecessors, which is the source of the greatest speed improvement. Some models can also run at faster bus speeds, which is the speed with which the CPU communicates with other computer components.

• Different packages Through the Pentium Pro, Intel's x86 CPUs have all used socketed designs, although the details of the sockets have varied from one CPU to another (see Figure 1.4). The Pentium II, however, introduced a different slot design, known as Slot 1. Some versions of the Pentium II and Celeron, however, are available in both socket (Socket 370) and Slot 1 formats.

Figure 1.4

Pentium II and III CPUs attach to the motherboard using a circuit board encased in a plastic shell, rather than using a socketed design like earlier x86 CPUs.

Figure 1.4

Pentium II and III CPUs attach to the motherboard using a circuit board encased in a plastic shell, rather than using a socketed design like earlier x86 CPUs.

If you plan to buy a new Intel CPU today, I recommend that you get a Pentium III, although high-end Pentium II and Celeron CPUs can be adequate for low-end systems. Pentium Pro CPUs are very hard to find and slow by today's standards. Celeron CPUs have small or no L2 caches, which hampers their performance. This isn't to say that anything less than a Pentium II is a poor CPU, of course; for many purposes, you don't need the fastest CPU available, and Linux runs fine on slower CPUs. For a new computer, you should purchase something that will remain viable for a while into the future.

You can get the most "bang for the buck" by purchasing a CPU that's a few notches below the fastest available. For instance, in early 2000, Pentium-III 700 CPUs were selling for about $850, but Pentium-III 600 CPUs were about $500 and Pentium-III 500 CPUs sold for about $300. The drop of the first 100MHz therefore saves $350, whereas the next 100MHz drop saves only $200.

Chapter 1

The very latest of the Intel Pentium III line is called Coppermine (although it doesn't use the copper trace technology invented by IBM and now used in PowerPC CPUs). Coppermine incorporates several advancements over previous Intel CPUs, such as a 133MHz motherboard bus, integration of the L2 cache into the main CPU wafer, and smaller circuitry. Aside from allowing higher motherboard bus speeds, these enhancements are largely invisible to you as a consumer, except that they produce a faster CPU. In fact, Intel chose not to release Coppermine under a new name; it's still a Pentium III CPU.

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