Everyone says the Intel 8086 processor has 29,000 tiny transistors. But I counted and found 19,618. Why the difference? It turns out that most counts include "potential" transistors as well as real ones. Let's take a look and find out why.🧵
Ken Shirriff on X: "Everyone says the Intel 8086 processor has 29,000 tiny transistors. But I counted and found 19,618. Why the difference? It turns out that most counts include "potential" transistors as well as real ones. Let's take a look and find out why.🧵 https://t.co/R7MqNLscBo"
A ROM (read-only memory) typically stores 1's and 0's by the presence or absence of a transistor for each bit. So the more 1's you have, the more transistors. It's inconvenient for the transistor count to change with the data, so "transistor sites" are usually counted.
But there are more complications. Output pins are driven by high-current driver transistors, built from multiple transistors in parallel. Do you count that as 12 transistors or 1 transistor?
Other ROMs, such as this constant ROM, are not exactly a grid but are slightly optimized. It's not clear if these potential transistors should be counted since there might not be room to fill in all of them. Also, some transistors act as diodes and many act as pull-up resistors.
So does the 8086 have 19,618 transistors or 29,277? It all depends on what you count. For more, see my blog post: righto.com/2023/01/counti…
I've written a bunch about the Intel 8086. My previous thread is here:
I've been staring at RPG map generation tools today, and my brain had trouble with the context switch :P