[monocasa]

Yes, for chips that need leading edge density like CPUs.

Of course the lines stay open after that for cases you've laid out, but there's a lot of financial reasons why that needs to be basically gravy train money at that point with the lines being fully amortized and having paid for themselves many times over.

[supernova87a]

For those retired lines, don't they sell them off to lower tier manufacturers pretty quickly? Say, within 5 years?

I am no expert but I didn't think the site would be just accumulating its n-1, n-2 generation lines to produce lower grade stuff in the same fab walls. They take up space that they want to continue producing top of line latest output. I thought.

[monocasa]

They're not really taking up space per se. For the cost of a fab, a new building (or new wing of a building) is peanuts.

Adding on to that, in a lot of ways the fab is the building, and at a bare minimum you'd be resetting a lot of the yield issues you fixed by moving it to a new space. So then you'd be left with an old node and yield issues, and what's the point of that?

There's also a ton of trade secret style IP still in the old nodes that could help a competitor, so why let it leave your property? Intel for instance is so into preventing trade market theft on the specifics of their nodes that they (at least used to) manually drill out every mobile device camera allowed in their fabs, in addition to the normal "no outside electronics past this point" security stations.