Introduction

Intel's Next Big Step

It's been over five years since Intel introduced a processor based on a dramatically new micro-architecture. Sure, the Pentium II and Pentium III brought a number of new improvements, but essentially, the core has remained the same since the introduction of the Pentium Pro in 1995.

Each new core has brought with it a number of innovative technologies that boosted system performance.

For instance, the original Pentium processor was Intel's first superscalar processor. Its superscalar pipeline added a second execution pipeline over the 486. As a result, it was capable of executing up to two instructions per clock cycle. Another added feature of the Pentium processor was its fully pipelined floating point unit. This gave the Pentium CPU an edge over its competition in 3D games such as Quake.

The Pentium Pro is most notable for its out-of-order speculative execution. This refers to the processor's ability to look at instructions ahead in the program and determine which instructions are dependent on each other. It then executes the instructions in the most efficient way possible while retiring them in the order they were originally written. Another feature of the Pentium Pro was its superpipelined architecture -- work was split into 12 stages, versus the five stages used in the original Pentium processor. This allowed the Pentium Pro processor to scale to higher clock speeds while it was still based on the same 0.35-micron manufacturing process.

Over the years Intel made a few changes to the original Pentium Pro architecture. With the Pentium II, the L2 cache was removed from the core for cost savings, but standard cache size increased to 512KB (Pentium Pro's with up to 1MB of L2 cache were available, but most shipped with 256KB). The Pentium II also introduced the Slot 1 interface as well as merged Intel's MMX instructions (and larger L1 cache) to the P6 core.

Today, Intel's latest CPU is the Pentium III. When it originally launched in February of last year, Intel simply added new instructions, known as Streaming SIMD Extensions (SSE). SSE was designed to enhance the performance of floating point applications, and as we saw in games such as Quake III, was a tremendous success for Intel.

So what's on tap from Intel for the Pentium 4? Besides its new rapid execution engine and execution trace cache, the Pentium 4 largely builds upon the basic ingredients of the P6 core and makes them better. Just what makes it so great? Lets take a look at its main features and see just what Intel's been up to the past few years.