London Banter - View Single Post - Last days of the 172s on the electrified GOBLIN

Roland Perry · January 31st 18, 06:05 AM posted to uk.transport.london

In message , at 14:55:47
on Tue, 30 Jan 2018, 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.

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

Would it be feasible to simply emulate all the old electronics and
computer components in software, running on a standard modern commodity
CPU? The modern CPU would be so much faster that it might deliver enough
performance to be able to precisely emulate the timing as well as the
behaviour of the old stuff.

How plausible is a software emulation of an NRN radio, and how would
one get it approved for use?

NRN radios

Typo, I meant RETB

weren't the problem. First of all, the later technology FM1000
type was type approved and in widespread use and they were standard enough
for a cottage industry to spring up keeping them going until NRNJ was
switched off recently. The problem was with the more specialised RETB radios
which were never made in such numbers and only used on a few lines, mainly
in the Highlands. Making a scratch-built CPC464 isn't a problem because it
doesn't have to be certified as in conformance to safety standards.

It *is* a problem, because the custom chip can't be made any more.

RETB radios are vital railway signalling components with a very strict
approvals regime.

Which both of us have mentioned earlier in the thread.
--
Roland Perry