Did people just... do this by hand (in software), transistor by transistor, or was it laid out programmatically in some sense? As in, were segments created algorithmically, then repeated to obtain the desired outcome? CPU design baffles me, especially considering there are 134 BILLION transistors or so in the latest i7 CPU. How does the team even keep track of, work on, or even load the files to WORK on the CPUs?
It's written in an HDL; IIRC both Intel and AMD use verilog. A modern core is on the order of a million or so lines of verilog.
Some of that will be hand placed, quite a bit will just be thrown at the synthesizer. Other parts like SRAM blocks will have their cad generated directly from a macro and a description of the block in question.
To further expound on this. ASIC (like AMD CPUs) is a lot like software work. The engineers that create a lot of the digital logic aren't dealing with individual transistors, instead they are saying "give me an accumulator for this section of code" and the HDL provides it. The definition of that module exists elsewhere and is shared throughout the system.
This is how the complexity can be wrangled.
Now, MOST of the work is automated for digital logic. However, we live in an analog world. So, there is (As far as I'm aware) still quite a bit of work for analog engineers to bend the analog reality into digital. In the real world, changing current creates magnetic fields which means you need definitions limiting voltages and defining how close a signal line can be to avoid cross talk. Square waves are hard to come by, so there's effort in timing and voltage bands to make sure you aren't registering a "1" when it should have been a "0".
Several of my professors were intel engineers. From what they told me, the ratios of employment were something like 100 digital engineers to 10 analog engineers to 1 Physicist/materials engineer.
They use EDA (Electronic Design Automation) software, there are only a handful of vendors, the largest probably being Mentor Graphics, now owned by Siemens. So, yes, they use automation to algorithmically build and track/resolve refactors as they design CPUs. CPUs are /generally/ block-type designs these days, so particular functions get repeated identically in different places and can be somewhat abstracted away in your EDA.
It's still enormously complex, and way more complex than the last time I touched this stuff more than 15 years ago.
