I do believe I remember reading articles that AMD used automation to help design Phenom-Bulldozer processor families because it was cheaper and faster than using engineers through the entire process, even though it resulted in massive die waste, inefficiency, and an inferior product,
I thought that was motivated by their desire to use the same toolchain and design flow for the CPU team as the GPU team was using, to facilitate the creation of APUs.
Anyway, you can't compare the state of the art in layout & routing between 15 years ago and today. BTW, that's also the backend part of the design process, and not at all what the article is talking about.
Zen was the first archetecture to go back to human designed from the ground up, which is why the gains were so massive over even Piledriver.
That's far too simplistic. Zen wasn't just a redesign, but a re-think about how AMD approached CPU architectures. Jim Keller described it as protocol-driven.
"We used to build computers such that you had a front end, a fetch, a dispatch, an execute, a load store, an L2 cache. If you looked at the boundaries between them, you'd see 100 wires doing random things that were dependent on exactly what cycle or what phase of the clock it was. Now these interfaces tend to look less like instruction boundaries – if I send an instruction from here to there, now I have a protocol. So the computer inside doesn't look like a big mess of stuff connected together, it looks like eight computers hooked together that do different things. There’s a fetch computer and a dispatch computer, an execution computer, and a floating-point computer. If you do that properly, you can change the floating-point without touching anything else.
That's less of an instruction set thing – it’s more ‘what was your design principle when you build it’, and then how did you do it. The thing is, if you get to a problem, you could say ‘if I could just have these five wires between these two boxes, I could get rid of this problem’. But every time you do that, every time you violate the abstraction layer, you've created a problem for future Jim. I've done that so many times, and like if you solve it properly, it would still be clean, but at some point if you hack it a little bit, then that kills you over time."
Source: https://www.anandtech.com/show/16762/an-anandtech-interview-with-jim-keller-laziest-person-at-tesla
Of course, I'm sure there were other differences, as well. But, the gains in Zen definitely weren't simply due to using full-custom layout.
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