The Intel 8086 Processor's Registers: From Chip to Transistors
owl writes:
https://www.righto.com/2020/07/the-intel-8086-processors-registers.html
The photo shows the silicon die of the 8086 processor under a microscope. The metal layer on top of the chip is visible, with the silicon hidden underneath. Around the outside edge, bond wires connect pads on the die to the chip's 40 external pins.
The highlighted region indicates the 8086's fifteen 16-bit registers and six bytes of instruction prefetch queue.1 Registers take up a significant portion of the die, even though they are just 36 bytes in total. Due to space limitations, early microprocessors had a relatively small number of registers; in comparison, a modern processor chip has kilobytes of registers and megabytes of cache storage.2
[...] The 8086 and other chips of that era were built from a type of transistor called NMOS. These chips consisted of a silicon substrate, which was "doped" by diffusion of arsenic or boron to form transistors. Above the silicon, polysilicon wiring created the gates of the transistors and wired components together. Finally, a metal layer on top provided more wiring. (Modern processors, in comparison, use CMOS technology, which combines NMOS and PMOS transistors, and they have many metal layers.)
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