If there are billions of transistors in a CPU, there is no chance that somebody designed every single one of them manually. Is their layout calculated or something?
In: 1270
Answer is abstraction. The design scales exponentially not linearly like you suggest. Combine several transistors into a logic operation device like AND or XOR. Then combine those logic devices into higher abstraction devices further until you get to ALU.
The designing of CPU is not linear – you don’t spend the the same amount of time per transistor. Design is exponential – you spend first say an hour designing a transistor device, then you spend another hour designing a logic device that consists of 10s or transistors, then the next hour you combine multiple logic devices into another abstraction level device that consists of 100s of transistors. For the purposes of this example you’ve spent 3 hours but have gotten already into 100s of transistors despite initially spending a whole hour on 1 transistor. In this way you can get to billions of transistors quite soon. Of course in the industry CPU design takes years, but the same concept applies.
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