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Comment by mrweasel | Hacker News Reader

Is the MAX really using a 286 CPU? Why would they pick that for a plane launched in 2014. I get that it's based on the 737 Next Gen, but they just opted to not update the electronics?

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The more you change, the more you need to recertify, the more it costs, the more time it takes, the less your shareholders profit.

This is the answer, and correct in many ways.

If the chips are cheap and easily available, and you know their failure modes, and they've been field tested for decades, why change?

It's very different from many software development attitudes, but remember that airframe manufacturers and avionics companies employ many people just to calculate risk and failure rates. The failure rates of these things are critical to the safety of your airframe.

Would probably add that it likely has reliable real-time constraints as part of this. While I can imagine simpler ARM and RISC-V chips having similar properties, depending on the application it would likely be hard to certify any modern CPU design for a lot of medical or aerospace applications.

That mindset is inevitably going to leave you in a ditch though. Either you run out of suppliers for the chip that are willing to produce on a shitty inefficient old node under certified conditions (mostly because it inevitably gets really expensive to keep the machines for production running!), or you run out of developers able and willing to write code for these old designs where the toolchain probably is also certified and has nowhere near close to the bells and whistles of modern IDEs or the automatic benefits from modern programming languages such as pointer safety.

Anything should have a replacement budget and timeline attached.

That's my gut feeling too but... I don't build certified airliners with lifespans of multiple decades for a living (or run companies that do).

All I know from having worked in an Airbus subsidiary for a couple of years is that their world is nothing like mine.

Make you wonder how long management figured they can keep using ancient technology, just to avoid updating certifications.

At a dinner with a team of Airbus folks we were working with at a previous job, they talked about how difficult it was getting to source CPUs for the A320 after 30 years.

It's definitely a "if it ain't broke don't fix it" thing, but I ask myself a similar question: at some point whoever is producing these chips is going to stop finding it worthwhile and end production, no?

But then I also assume the people who work on these things know arguably infinitely more than I do.

They do :)

And if the companies who produce these chips continue to make a healthy profit, why would they stop?

The scenario that comes to my mind is: these chips had a lot of potential customers 30 years ago, and now may be down to just one or two customers left buying too few units to make it worthwhile.

Presumably, they have "guaranteed" buyers but also, if so, why would Airbus have issues sourcing CPUs, for example?

> […] too few units to make it worthwhile.

Not if the price of those units are really high.

Yeah, maybe the difficulty for the buyers is not getting price-gouged by a sole remaining supplier.

But no one is producing 286 chips anymore, that's part of the problem Boing has. The chips fail, because they are used and old. Or is someone besides Intel making them?

Forever if someone keeps making new chips.

No. It is an FCP-2002. See https://news.ycombinator.com/item?id=23763398

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