On 30/01/2018 10:06, Roland Perry wrote:
In message , at 09:08:18 on Tue, 30 Jan
2018, Someone Somewhere remarked:


Nothing that was manufactered is unmanufacturable - it may not be
reasonably economic to do so,Â* or in certain cases legislation may
prevent it (lead etc) but if it was built once, it could be built again.

There are whole generations of custom-chips which aren't manufacturable
any more. Either the company which made them originally has gone out of
business/disappeared within another that's not longer in the foundry
business, or the tools and machinery required to produce a new batch
have long since been consigned to the dustbin of history.

A handful of generic chips may still be available, so you could perhaps
get a brand-new Z80 equivalent/clone processor chip to build a replica
Amstrad CPC464, but good luck getting Ferranti or SGS to make you a
fresh one of the ULAs.

You could still recreate them with enough time and money - they aren't
made of unobtanium - so it's economics. Now to rebuild the Ferranti fab
may be a ludicrous amount of money, but it's theoretically possible.

Or of course you could use FPGAs to do the same thing these days.