The Evolution of the x86 Computer Architecture
We know the first x86 chip was the 8086, followed by the 80286, 80386, 80486, Pentium… This article uses many images to walk everyone through the development history of x86 computers, so you can understand when each part of today’s computers was added, and what historical event each upgrade was made to be compatible with.
The Intel 8086 had a 20–bit address line.
It could address 1 MB of memory.
The Intel 80286 had a 24–bit address line.
It could address 16 MB of memory.
The Intel 80386 had a 32–bit address line.
It could address 4 GB of memory.
8086
The image below shows the IBM PC — it looks really cool, I’d love to have one.
IBM PC (IBM Personal Computer 5150) was born in 1981. It held the top spot in the IT field for a long time and was IBM’s first product.
Two years later, the IBM PC XT extended the IBM PC and used the 8088 processor:
Below is the circuit diagram of the IBM PC XT upgrade board, which used the 8088:
The IBM PC 5160’s main circuit board was the motherboard, integrating a 4.77 MHz Intel 8088 processor and 64 KB of RAM (expandable up to 256 KB). The chassis came standard with 5 expansion slots, had a built-in single/dual floppy drive but no hard drive support, and connected to the motherboard via cables. The standard storage medium was a cassette tape, and the ROM was loaded with Microsoft BASIC.
To optimize the task-processing performance of this product, IBM also used the NEC V20 processor to boost runtime performance and introduced the Intel 8087 coprocessor to improve its math-processing capability. An interesting detail: this product came standard with a monochrome display, but the built-in color graphics adapter actually supported a regular TV as the image output device.
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In 1985 Toshiba launched the first laptop computer, the T1100. The ancient Toshiba T1100 used an Intel 8086 processor and 512 KB of RAM. Despite the small 9-inch screen and external hard drive, it weighed nearly 3 kg. But keep in mind that ordinary desktops at the time weighed tens of kilograms — those “big boys.” A 3 kg computer was already a legend back then.
80286
An 80286-based computer produced by IBM in 1986.
The image below shows the upgraded version of the PC XT 286, the PC AT. It used an 80286 CPU, ran MS-DOS 3.0, had 256 KB (first generation) or 512 KB (second generation) of RAM, supported 5.25-inch floppy disks, and supported a 20 MB hard drive:
The image below is a block diagram of the 80286. As you can see from the diagram, compared to the 8086 computer, the memory is no longer connected directly to the CPU — it hangs off the L2 cache, the L2 cache hangs off the DRAM and L2 cache controller, and the L2 cache controller connects directly to the CPU’s system bus.
Pentium 4
Celeron M
Intel Core
Intel Core gen 5
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