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by zozbot234 1809 days ago
Note that Google has open sourced a full set of design rules for a 130nm process (codenamed SkyWater), making fully open chip designs also possible for this finer process. 130nm was current in the very early 2000s, so it should be possible to achieve interesting results with it.
1 comments
swiley 1809 days ago
Didn't they require some closed logic between your stuff and all of the I/O?
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KirillPanov 1809 days ago
Yes, and they still do. They've got a Management-Engine type layer that you are forbidden to remove or modify in any way, even if you pay the full $10k and do not accept any subsidies.

So many people asked about this that the foundry had to make a FAQ about it:

https://www.skywatertechnology.com/ufaqs/can-i-customize-the...

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zozbot234 1809 days ago
This impacts the fab itself, but the design rules can still be usable elsewhere since they've been released openly.
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KirillPanov 1809 days ago
Use them where, exactly?

Your comment glosses over a ton of critical details.

The most important of them being that even on such an old technology generation (180nm-110nm) no two fabs are so compatible that you can send a GDS designed for one of them to the other unless (a) one of them licensed their process from the other, like IBM/GloFo/Samsung back in the 2010s or (b) you planned for this in advance and designed a custom "least common denominator" process (like MOSIS SCMOS) to target which means making very large performance sacrifices. The (b) approach is much harder than it looks; I know of no examples other than MOSIS SCMOS, and in spite of being the pioneer experts at doing this they had a hard time at 180nm and failed on the following (90nm) generation.

The other, lesser, problem is that no foundry will let you even submit a GDS without signing their NDA. Even if you swear to them that you don't need their design rules for some reason. They don't care. NDA or no chips, not up for discussion. In fact, technically SkyWater still works this way -- to avoid the NDA you must submit through eFabless, not directly to the foundry (maybe this will change someday) and eFabless signed their NDA, then (obviously) negotiated a waiver. So saying "you can work around this problem that the only no-NDA foundry has by just going to another foundry" because there are no other no-NDA foundries, nor are there any on the horizon.

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zozbot234 1809 days ago
> (a) one of them licensed their process from the other, like IBM/GloFo/Samsung back in the 2010s or (b) you planned for this in advance and designed a custom "least common denominator" process (like MOSIS SCMOS) to target which means making very large performance sacrifices.

The availability of open design rules improves the feasibility of either approach. Any other foundry implementing a 130nm process will be able to refer to the open rules quite directly, with no strings attached - and they will also have very clear incentives to push in that direction. So no, this is not a full fab process, but it's getting remarkably close compared to what we had before.

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