Comment by shoo | Hacker News Reader

Comment by shoo | Hacker News Reader

> The next challenge was the choice of the operating system for the host platform. We choose Windows XP because the Proprietary Co-processor card at the heart of the system was especially adapted to run under Windows XP. This operating system is not the best ‘choice for real time applications’ therefore special attention was required in the method of integration. Running the Windows operating system in cut down mode by disabling unnecessary apps and keeping it free of all ‘gadgets’ (Office software etc.) increased the system stability sufficiently

> Due to the core software limitation (no source code available) we were compelled to integrate some original PDP-11 computer cards into the final product and this resulted in a hybrid PC platform. There are two very distinct hardware technologies in use in each complete system. The PC environment which is the host platform and the DEC environment which is the ‘legacy’ system. The connection is made using a proprietary Unibus adapter that links the Osprey co-processor to the short Unibus. This Unibus which is totally contained inside the special PC housing allows us to retain some key legacy DEC PDP-11 cards that in turn deceives the software ‘to think’ it is still running in a full DEC system in terms of timing. A marriage of ‘old’ and ‘new’ was borne

One of God's own prototypes. A high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.

The PDP-11 bus is really simple, it's easy to whip up custom cards with a handful of TTL chips. Also DEC used to sell all the parts separately, including backplanes which had a wirewrap pin on every contact. As a result, integrating a PDP-11 (more usually LSI-11 on QBus) into a system was quite simple - bolt a backplane to the end of a 19" rack of DIN41612 connectors and wirewrap the two together (we did systems with 10 or more motor control cards, each with around 100 TTL chips on).

A particularly nice feature of the bus is that it was memory-mapped, and everything (memory as well as custom hardware) would send an ACK signal back to the processor when addressed; addressing a non-existent memory location would cause a bus trap.

Edit: The bus is simple enough that creating an arduino, say, interface to drive old DEC cards woould not be hard. I'll keep that thought for the next time someone needs their nuclear power station updating [0].

[0] https://news.ycombinator.com/item?id=5904191

Am I the only one to whom the phrases "windows XP" and "trains" in the same sentence makes your blood chill a little? Also -- what about virtualizing the OS with pcie passthrough and being able to regularly snapshot it / migrate as running to other hosts (if they have enough odd cards, etc)

I once worked on a project migrating a central component used on trains from Windows 95 to Windows XP... this year.

XP had a solid base in NT. If you don't use the desktop it is very solid. I wouldn't connect it to the internet, but I wouldn't do that anyway .

I know of a hospital still running a Meditech MAGIC system for historical data purposes. The system is a collection of IBM servers, all running Windows Server 2000.

Meditech, however, uses its own network stack on the OS, replacing all Windows networking components with a Meditech MAGIC driver, and Meditech's own software then controls TCP/IP inside its emulation that runs on top of 2000 in usermode. It's amazing how well put together the stack is that this could be (fairly easily) migrated up to a Server 2012-era box* and still work the exact same way.

*(that I know of - I assume they have newer support by now)

To this day there are probably thousands to tens of thousands of SCADA and other industrial control systems around the world running on XP. It's an incredibly stable system when configured properly.

> We choose Windows XP because the Proprietary Co-processor card at the heart of the system was especially adapted to run under Windows XP.

But why did they choose such a card in the first place?

Because it was capable of running the existing (unchangable) software.

Finding replacement parts will be interesting. I hope they have a nice maintenance contract.

Almost worthy of an "Hey Boss, I got it working! Come look, it's neat!"

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