To celebrate the 42nd anniversary of the 8086 and the debut of the x86 architecture, we’re bumping our previous retrospectives on some of Intel’s most important CPU designs. In this article, we’ve rounded up the first decades of history, from the 4004 in 1971 to the Pentium Pro in 1994. This period covers the first two eras of Moore’s Law (a concept we’ve discussed elsewhere), in which discrete capabilities were rapidly integrated on to a single contiguous wafer, and then as microprocessor transistor counts and clock speeds continued to rise.
Today, x86 chips are the backbone of modern computing. ARM may dominate the smartphone industry, but the cloud-based services and platforms that smartphones rely on are sitting in data centers running on x86-based hardware. What’s surprising, looking back, is that no one at Intel had even an inkling that this was going to take place. Intel had sunk its hopes and dreams into the i432APX, a 32-bit microprocessor with a radically different design than anything the company had tried before. Early sales of the 8086 and 8088 weren’t very strong, since the entire computer market was facing something of a hardware glut. Intel’s Operation Crush, an aggressive marketing and support effort around the 8086, helped change that and caught IBM’s attention in the process.
Enter IBM. When Big Blue decided to build its first PC, it narrowed the field to three choices: Motorola’s 68000, the Intel 8086, and the Intel 8088. Because the 8088 and 8086 were compatible with each other, it ultimately didn’t matter which Intel CPU IBM picked. IBM was more familiar with Intel than Motorola and Microsoft had a BASIC interpreter with x86 support already baked in. If IBM had gone the other way, we might well be sitting here talking about the rise of “Motosoft” instead of “Mintel.” IBM’s decision to back Intel shaped the future of computing, and Intel’s future processors. Over the next few years, OEMs like Compaq brought new systems to market, powered by new, more advanced x86 CPUs.
Below, we’ll discuss the next series of Intel CPUs, starting with the 80286 and running through the Pentium Pro. The 80186, while it technically existed, was actually primarily used as an embedded microcontroller rather than a PC CPU (with a bare handful of exceptions). For most, the line of succession jumped from the 8086/8088 to the 80286.
The 8086 to Pentium can arguably be grouped as a single family of products, albeit a family that evolved enormously in less than 20 years. All of these chips executed native x86 instructions using what we now call in-order execution (prior to the invention of out-of-order execution we just called this “execution.”) Intel rose to dominate the personal computing market on the strength of these cores. In October 1985, the fastest 80386DX was clocked at 12MHz. By June of 1995, the Pentium 133 was on-sale — a greater-than 10x speed improvement, on top of all the architectural improvements, in just a decade.
By this point, Intel had already largely conquered the personal computer market and begun making early inroads into the workstation and data center spaces, but the bulk of the market still belonged to various RISC architectures backed by entrenched players like Sun, MIPS, and HP. Intel wanted to expand into data centers and professional workstations, but to do that it needed a CPU architecture that would allow it to compete against these high-end workstation chips on absolute performance. Intel had added manufacturing capacity through the 1980s and 1990s, and any new chip needed to do more than simply boost performance — it needed to be a CPU that could leverage Intel’s growing economies of scale.
The Pentium Pro and its descendants were that CPU. We’ll discuss how they evolved — and the features they brought to market — in Part 2.
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