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Comment by morphle | Hacker News Reader

no, the mask must be made within the tight rules of the proprietary (and very secret) PDK of the TSMC Fab for that node. Just getting it certified that it fits the rules will cost millions.

https://en.wikipedia.org/wiki/Process_design_kit

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How were the Parallax Propeller guys able to do it? They have a Propeller2 that is in either 40nm or 28nm, IIRC.

Because those are now trailing edge nodes, so cheaper and easier entry for everybody.

Interesting. What is the granularity? Is it logic gates, or transistors?

the granularity is at all levels: standard cells (=gates), transistor shapes, metal layer shapes down to groups of atoms (for quantum dots).

Are all fabs like this?

It's probably more of a node thing than a fab thing. You would have a much easier time getting the fab to do random stuff for you on a legacy node compared to a leading edge node.

Leading edge nodes are basically black magic and are right on the edge of working vs producing broken chips.

You as a customer would never want to be in a position where you are solely responsible for yields.

There are only a few Fabs with nodes smaller than 28nm. Yes, all fabs are like that, with exception of a few experimental tiny labs at research institutes or universities.

There are open-source PDKs[0] for education, research, and R&D - but they extremely rare and decades behind state-of-the-art.

Nobody wants to give away trade secrets, so everything remains proprietary and behind an NDA until it has become completely obsolete.

[0]: https://www.skywatertechnology.com/sky130-open-source-pdk/

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