In message , at 11:19:55 on Tue, 30 Jan
2018, Someone Somewhere remarked:

Nothing that was manufactered is unmanufacturable - it may not be
reasonably economic to do so,* 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.

I thought we were discussing things which *were* [claimed to be]
economically feasible. Like restarting Electrostar production.

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

If you can reverse engineer the circuitry inside the ULA.

Can you make a radio transceiver out of FPGA's?
--
Roland Perry