In the world of today’s high performance CPUs, major architectural changes don’t happen often. Iterating off a proven base is safer, cheaper, and faster than attempting to massively rework the basics of how a CPU fetches and executes instructions. But more than 20 years ago, things hadn’t settled down yet. Intel made two attempts to replace its solid but aging P6 microarchitecture with something completely different. One was Itanium, which avoided the complexity associated with out-of-order execution and variable length decode to deliver very wide in-order execution.
Pentium 4 was the other, and we’ll be taking a look at it in this article. Its microarchitecture, called Netburst, targeted very high clock speeds using a long pipeline. Alongside this key feature, it brought a wide range of innovative architectural features. As we all know, it didn’t quite pan out the way Intel would have liked. But this architecture was an important learning experience for Intel, and was arguably key to the company’s later success.
The Pentium 4 era was wild, with insane promises Intel could not fulfill, but at the same time, an are of innovation and progress that would help Intel in later years. Fascinating time.
I remember those times, and Netburst was such a failure, they had to go back to the P6 for Pentium M, then used that as the basis for the original core architecture. Not much remained of the Netburst architecture. It was a failure, and so was Itanium. It was AMD who really saved Intel’s butt, by cross licensing x64 and multi core designs.