Introduction

Pentium III is back!

If you recall our original Pentium 4 Performance Preview, at the end of the article we were left with mixed feelings about the Pentium 4. In terms of performance, Pentium 4 trailed behind Athlon in most of our benchmarks, and came with huge infrastructure changes (as is expected with a CPU based on an entirely new microarchitecture). In the end we were left wishing Intel had instead devoted more time and resources to tweaking the Pentium III's latest core at the time, internally known as "Coppermine".

In particular, features such as a 200MHz front-side bus and larger onboard cache size were rumored for future Pentium III cores. These additions would have brought more performance at a given clock speed than previous Pentium III processors, and allowed the chip to compete more favorably with AMD's Athlon CPU from a features perspective - while Pentium III offered 288KB of onboard cache, Athlon contained 384KB. In addition, Athlon's front-side bus effectively operated at speeds of 200MHz, and later 266MHz, twice as fast as Pentium III's bus speed of 100MHz or 133MHz (depending on the processor). Instead, Intel unleashed its Pentium 4 processor.

While Pentium III was merely an extension of the Pentium II core (initially, the only addition was Intel's new SSE instructions), Pentium 4 brought with it Intel's 7th generation Netburst microarchitecture. Arguably, the feature that ends up being discussed the most is the Pentium 4's long 20-stage pipeline - twice the length of Pentium III.

Our 1.2GHz Pentium III system

A closer look at the cooling unit we used

As you probably know by now, Pentium 4's 20-stage pipeline allows the processor to reach higher clock speeds than Pentium III at the cost of less work performed per clock cycle. As Intel found out last year, Coppermine processors built on Intel's 0.18-micron manufacturing process don't yield well at clock speeds beyond 1GHz: supply simply isn't able to keep up with demand. In addition, stability problems at 1.13GHz were discovered, leading to a processor recall last summer. Fortunately for Intel, shipments of Pentium III 1.13GHz parts were limited, leaving little impact on the company's balance sheet. But the recall lead to an embarrassing situation for the company, as AMD was able to supply the market with Athlon parts of 1.1, and later 1.2GHz.

Considering all this, some would argue that Pentium 4 showed up at just the right time for Intel. With Pentium III stuck at 1GHz, a new microarchitecture was needed to hit speeds of 1.5GHz and higher. While this is certainly true, we've all been curious to see what might have happened had Intel stuck with its Pentium III core a little longer. Thanks to Intel's new 0.13-micron manufacturing process, the public gets to see what might have been.

While the desktop version of the final product isn't quite as ambitious as some of the early rumors indicated, we were pleasantly surprised by one aspect of Intel's latest Pentium III. But first, lets discuss the changes implemented in the new core.