Anybody out there?

Probably true for electronic assembly equipment; less true for paper mills...

There are still stories of Apple II's being used in process control and lab automation--and even the occasional veterinary office. ;-)

"If it ain't broke, don't fix it."

AFAIK UK ATC is still on a pair of 370/195s, arranged to give automatic failover. The Swanwick ATC system, currently maintained by Lockheed Martin, was originally written by IBM, so it certainly isn't running on PDP11s or even VAXen.

On Fri, 18 Sep 2015 22:05:34 +0100, The Natural Philosopher declaimed the following:

Unless they rely upon custom boards that interface with the PDP-11 backplane, I suspect they'll be replaced with some servers running a virtual machine emulation of the PDP-11...

As I understand it, that's already been the path of a lot of stuff associated with NoSuchAgency... In this case, VAX/Alpha OpenVMS applications that would cost too much to redevelop as native on modern hardware -- so run an emulated OpenVMS system (though I still wonder how they emulate the four-levels of VAX protection, on machines that normally only support user/super levels){and VAX quad-floats probably run slow also... except for the system doing the emulation likely running much faster than the original hardware}

How do they fix them when they *do* break? No computer runs forever. I can't see how the Nuke plants could be running on PDP11s. They haven't been made for decades. Where do they get their spares?

You need some bars of TTL. In an emergency, most can be replaced with

A couple of years ago, I was summoned to a paper mill to mend their PDP-11. The cure was one 74LS00. It seemed that the biggest problem was to find somebody still remembering and understanding the computer.

I understand the problem of rewriting software that is part of a critical system. It can be *enormously* expensive. When a system is a custom system, it can be very hard to replace it with generic systems. I met some guys from NASA a while back who were really just technicians. They talked about a TTL level system for collecting and distributing telemetry that could not be replaced by networked workstations designed decades later.

It is hard to imaging that it would still be economical to maintain computers that you need to fix at the chip level. But if the alternative is spending a million dollars to rewrite the software... I guess ancient hardware is the way to go. I just wish I had held onto my LSI-11. It might be worth something now.

Try googling for pdp11 emulators. You'll find many - with commercial support. You'll even find PC ISA/PCI cards that emulate the PDP11 buses and interfaces. There is still a market for this stuff in old industrial control systems.

A PDP11 is not that complex - unlike modern PCs it's easily within the scope of a single person to understand the entire circuitry - if neccessary. Who many people still do, or are willing to learn may be another matter.

Gordon

Oh, I know how simple they are. Very similar to the MSP430, just a LOT bigger.

I can't speak for PDP11s, but Apple II's were all LS TTL (except for the processor) and were not only prodigiously reliable, but easy to repair.

The switching power supply was perhaps the most likely subsystem to fail, but they are easily replaced.

On Sat, 19 Sep 2015 14:31:42 -0400, rickman declaimed the following:

Please... I already have BASICStamp 2, 2p, and 2px boards... a few Propeller boards, Arduino Uno, Mega2560, Esplora, and Due, two brand new BeagleBone Blacks, and TIVA 123, 1294, and 129E launchpads...

And you are making me think I should add an MSP430 to the stash?

Has anyone ported a MIL-STD 1750A compliant system to an Altoids tin yet?

Do you know how many WWII Merlin engines there are still in the world?

Despite none having been made since about 1950?

FFS a DEC PDP is just TTL logic and old fashioned DRAM surely?

Oh it started that way but eventually they made a chip, with Harris, and the russians ripped it off as well.

Really they are not worth much.

As you point out, the investment is in the systems and the software that surrounds them/runs on them..

My old DG Nova 1200 was pure TTL with a single 74189 ALU. That meant each arithmetic op on 16bit words was processed in 4x 4bit nibbles. I still regret having to get rid of it.

On Sun, 20 Sep 2015 10:05:56 +0100, The Natural Philosopher declaimed the following:

Everything I've found indicates the LSI version was initially done by Western Digital...

Seems even Heathkit had one for sale:

That's the one I had. The CPU board and the backplane were the same as in the DEC units and everything else was designed by Heath, including the optional paper tape reader/punch. Eventually I installed 8 inch floppy drives. It ran RT-11.

The Harris chip from memory was a PDP-8 architecture.

Then DEC made their own chips in their own foundry, leading to the Alpha.

Having messed around with LSI-11, T11, J11 not quite microVax in my days there.

The new owners of OpenVMS (VMS Software Inc

On Mon, 21 Sep 2015 23:12:40 +0000 (UTC), David James declaimed the following:

Wonder what that's done to the "hobbyist" license that used to be possible.

I believe it is still currently available and I think VSI have said they plan to continue something similar.

There has been a lot of discussion on the comp.os.vms newsgroup over the last 18 months or so.