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Processors are probably the most single interesting piece of hardware in your computer. They have a rich and neat history history, dating all the way back to 1971 with the first commercially available microprocessor, the Intel 4004. As you can imagine and have no doubt seen yourself, since then, technology has improved by leaps and bounds.

We’re going to show you a history of the processor, starting with the Intel 8086. It was the processor IBM chose for the first PC and only has a neat history from then on out.

Editor’s Note: This article was originally published in 2001, but as of December 2016, we’ve updated it to include new advancements in the field since then.

Intel 8086

CPUs have gone through many changes through the few years since Intel came out with the first one. IBM chose Intel’s 8088 processor for the brains of the first PC. This choice by IBM is what made Intel the perceived leader of the CPU market. Intel remains the perceived leader of microprocessor development. While newer contenders have developed their own technologies for their own processors, Intel continues to remain more than a viable source of new technology in this market, with the ever-growing AMD nipping at their heels.

The first four generations of Intel processor took on the “8” as the series name, which is why the technical types refer to this family of chips as the 8088, 8086, and 80186. This goes right on up to the 80486, or simply the 486. The following chips are considered the dinosaurs of the computer world. PC’s based on these processors are the kind that usually sit around in the garage or warehouse collecting dust. They are not of much use anymore, but us geeks don’t like throwing them out because they still work. You know who you are.

• Intel 8086 (1978)
  This chip was skipped over for the original PC, but was used in a few later computers that didn’t amount to much. It was a true 16-bit processor and talked with its cards via a 16 wire data connection. The chip contained 29,000 transistors and 20 address lines that gave it the ability to talk with up to 1 MB of RAM. What is interesting is that the designers of the time never suspected anyone would ever need more than 1 MB of RAM. The chip was available in 5, 6,, 8, and 10 MHz versions.
• Intel 8088 (1979)
  The 8088 is, for all practical purposes, identical to the 8086. The only difference is that it handles its address lines differently than the 8086. This chip was the one that was chosen for the first IBM PC, and like the 8086, it is able to work with the 8087 math coprocessor chip.
• NEC V20 and V30 (1981)
  Clones of the 8088 and 8086. They are supposed to be about 30% faster than the Intel ones, though.
• Intel 80186 (1980)
  The 186 was a popular chip. Many versions have been developed in its history. Buyers could choose from CHMOS or HMOS, 8-bit or 16-bit versions, depending on what they needed. A CHMOS chip could run at twice the clock speed and at one fourth the power of the HMOS chip. In 1990, Intel came out with the Enhanced 186 family. They all shared a common core design. They had a 1-micron core design and ran at about 25MHz at 3 volts. The 80186 contained a high level of integration, with the system controller, interrupt controller, DMA controller and timing circuitry right on the CPU. Despite this, the 186 never found itself in a personal computer.
• Intel 80286 (1982)
  A 16-bit, 134,000 transistor processor capable of addressing up to 16 MB of RAM. In addition to the increased physical memory support, this chip is able to work with virtual memory, thereby allowing much for expandability. The 286 was the first “real” processor. It introduced the concept of protected mode. This is the ability to multitask, having different programs run separately but at the same time. This ability was not taken advantage of by DOS, but future Operating Systems, such as Windows, could play with this new feature. On the the drawbacks of this ability, though, was that while it could switch from real mode to protected mode (real mode was intended to make it backwards compatible with the 8088’s), it could not switch back to real mode without a warm reboot. This chip was used by IBM in its Advanced Technology PC/AT and was used in a lot of IBM-compatibles. It ran at 8, 10, and 12.5 MHz, but later editions of the chip ran as high as 20 MHz. While these chips are considered paperweights today, they were rather revolutionary for the time period.
• Intel 386 (1985 – 1990)
  The 386 signified a major increase in technology from Intel. The 386 was a 32-bit processor, meaning its data throughput was immediately twice that of the 286. Containing 275,000 transistors, the 80386DX processor came in 16, 20, 25, and 33 MHz versions. The 32-bit address bus allowed the chip to work with a full 4 GB of RAM and a staggering 64 TB of virtual memory. In addition, the 386 was the first chip to use instruction pipelining, which allows the processor to start working on the next instruction before the previous one is complete. While the chip could run in both real and protected mode (like the 286), it could also run in virtual real mode, allowing several reasl mode sessions to be run at a time. A multi-tasking operating system such as Windows was necessary to do this, though. In 1988, Intel released the 386SX, which was basically a low-fat version of the 386. It used the 16-bit data bus rather than the 32-bit, and it was slower, but it thus used less power and thus enabled Intel to promote the chip into desktops and even portables. In 1990, Intel released the 80386SL, which was basically an 855,00 transistor version of the 386SX processor, with ISA compatibility and power management circuitry.
  386 chips were designed to be user friendly. All chips in the family were pin-for-pin compatible and they were binary compatible with the previous 186 chips, meaning that users didn’t have to get new software to use it. Also, the 386 offered power friendly features such as low voltage requirements and System Management Mode (SMM) which could power down various components to save power. Overall, this chip was a big step for chip development. It set the standard that many later chips would follow. It offered a simple design which developers could easily design for.

Intel 486 (1989 – 1994)

The 80486DX was released in 1989. It was a 32-bit processor containing 1.2 million transistors. It had the same memory capacity as the 386 (both were 32-bit) but offered twice the speed at 26.9 million instructions per second (MIPS) at 33 MHz. There are some improvements here, though, beyond just speed. The 486 was the first to have an integrated floating point unit (FPU) to replace the normally separate math coprocessor (not all flavors of the 486 had this, though). It also contained an integrated 8 KB on-die cache. This increases speed by using the instruction pipelining to predict the next instructions and then storing them in the cache. Then, when the processor needs that data, it pulls it out of the cache rather than using the necessary overhead to access the external memory. Also, the 486 came in 5 volt and 3 volt versions, allowing flexibility for desktops and laptops.

The 486 chip was the first processor from Intel that was designed to be upgradeable. Previous processors were not designed this way, so when the processor became obsolete, the entire motherboard needed to be replaced. With the 486, the same CPU socket could accommodate several different flavors of the 486. Initial 486 offerings were designed to be able to be upgraded using “OverDrive” technology. This means you can insert a chip with a faster internal clock into the existing system. Not all 486 systems could use OverDrive, since it takes a certain type of motherboard to support it.

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The first member of the 486 family was the i486DX, but in 1991 they released the 486SX and 486DX/50. Both chips were basically the same, except that the 486SX version had the math coprocessor disabled (yes, it was there, just turned off). The 486SX was, of course, slower than its DX cousin, but the resulting reduced cost and power lent itself to faster sales and movement into the laptop market. The 486DX/50 was simply a 50MHz version of the original 486. The DX could not support future OverDrives while the SX processor could.

In 1992, Intel released the next wave of 486’s making use of OverDrive technology. The first models were the i486DX2/50 and i486DX2/66. The extra “2” in the names indicate that the normal clock speed of the processor is being effectively doubled using OverDrive, so the 486DX2/50 is a 25MHz chip being doubled to 50MHz. The slower base speed allowed the chip to work with existing motherboard designs, but allowed the chip internally to operate at the increased speed, thereby increasing performance.

Also in 1992, Intel put out the 486SL. It was virtually identical to vintage 486 processors, but it contained 1.4 million transistors. The extra innards were used by its internal power management circuitry, optimizing it for mobile use. From there, Intel released various 486 flavors, mixing SL’s with SX’s and DX’s at a variety of clock speeds. By 1994, they were rounding out their continued development of the 486 family with the DX4 Overdrive processors. While you might think these were 4X clock quadruplers, they were actually 3X triplers, allowing a 33 MHz processor to operate internally at 100 MHz.

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