Intel is the most important microprocessor manufacturer in the world. Architecture after architecture, here is the history of its CPUs. Intel 4004 The first microprocessor sold by Intel was the 4-bit 4004 in 1971. It was designed to work together with three other microchips – the ROM 4001, the RAM 4002 and the Shift Register 4003. The 4004 performed calculations, while the others were crucial to make the processor work. The 4004 was mainly used in computers and similar devices, and was not meant to end up inside computers. Its maximum frequency was 740 KHz. The 4004 was followed by a similar processor, the 4040, an improved variant with an extensive instruction set and greater performance. 8008 and 8080 The 4004 allowed Intel to make a name for itself in the microprocessor sector. To capitalize on the situation, Intel introduced a new line of 8-bit processors. The 8008 came in 1972, followed by 8080 in 1974 and 8085 in 1975. Although the 8008 was Intel’s first 8-bit processor, it was not as important as its predecessor and its successor. It was faster than 4004 thanks to its ability to process 8-bit data, but had a rather conservative frequency, between 200 and 800 KHz, and consequently its performance was not entirely convincing. 8008 was produced with 10 micrometer transistors. The 8080 was more successful: it was 8008 at 6 micrometers and included new instructions. This allowed the company more than double the frequencies: the best 8080 chips arrived in 1974 with a frequency of 2 MHz. The 8080 was integrated into many devices and this brought many software developers, such as the then young Microsoft, to focus on Intel processors. 8086 The 8086 was the first x86 processor. This 16-bit chip could handle 1 MB of memory using a 20-bit external bus. The clock frequency was 4.77 MHz, decidedly low, considering that at the end of his career this processor reached 10 MHz. Thanks to the 16 bits he managed two 8-bit instructions simultaneously. 8086 used the first revision of the ISA x86, still used by AMD and Intel. 80186 and 80188 All 8086 were followed by several other processors based on the same 16-bit architecture. The first was 80186. Intel migrated several hardware components usually located on the motherboard inside the CPU, such as the clock generator, the interrupt controller and the timer. Thanks to the integration of these components into the processor the 80186 proved to be several times faster than the 8086. Intel also increased the frequency to get more performance. The 80188 was a less expensive variant with a halved bus. 80286 Presented in the same year as 80186, 80286 was three times faster than 8086 at the same frequency. It could handle 16 MB of memory thanks to a 24-bit address bus. It was the first x86 with a memory management unit (MMU), which allowed virtual memory management. Like 8086, it did not have a floating-point unit (FPU): it relied on a x87 co-processor (80287). The maximum frequency touched 12.5 MHz.