But it's not just about cost, the amount of extra resource -- meaning, engineers! -- needed to support both BSPD and FSPD processes is huge because so many things are different. For starters the layouts are completely different so all IP (both internally and externally sourced) has to be rebuilt from scratch, and it's not just a few layout tweaks it's a major rethink -- plus the extraction is different, thermal properties are very different, libraries (standard cell and SRAM) have to be redone from scratch, tool costs double, customer support effort doubles. You also have to duplicate all the process qualification/reliability analysis because the processes are physically fundamentally different, and this alone is a massive effort and takes a lot of time and wafers to do.
Intel are already likely to be stretched in all these areas just to support BSPD because traditionally they only had to support internal design teams (so crappy documentation is "OK"), much more effort/resource is needed to properly support external customers -- been there in the past, got the T-shirt. Suggesting that they could easily do all this again for FSPD is not credible, they'd end up with terrible support for both processes instead of barely adequate support for one -- TSMC have being doing all this for years on multiple processes, but that doesn't mean Intel can do the same...
It doesn't matter how much Intel might *want* do support both, the question is whether they *can* support both -- and I don't think they can, at least not today.
There's also the question of why they would realistically want to do this, because all the things that FSPD customers are looking for -- fast TTM, strong IP ecosystem, low cost, high yield, high density, quick TAT -- are the things that TSMC is *very* good at (which is why everyone uses them) and Intel is historically bad at (and still not competitive today). Fighting an opponent on a battleground where they're strong and you're weak is never going to end well... :-(
People who don't understand the huge differences between the two processes are grossly underestimating the cost and difficulty of supporting both, see post from
@MKWVentures above... ;-)