[kristopolous]

When we go back to the moon, I wouldn't be surprised if Zilog-Z80s were a major part of the hardware. Well known, well understood, predictable hardware goes a long way. There's a bunch of other considerations in outer space and z80s have proven robust and reliable there. Also I'd expect a bunch of Kermit and Xmodem to be used as well.

[GlenTheMachine]

They won’t be. We will use RAD750’s, the flight qualified variant of the PowerPC architecture. That’s the standard high end flight processor.

https://www.petervis.com/Vintage%20Chips/PowerPC%20750/RAD75...

The next generation (at least according to NASA) will be RISC-V variants:

https://www.zdnet.com/article/nasa-has-chosen-these-cpus-to-...

[johnwalkr]

I wouldn't call it the standard, it's just used in designs with legacy to avoid the huge cost of re-qualification of hardware and software. It's infeasible a lot of times due to cost and power consumption. I work in the private sector in space (lunar exploration actually) and everyone is qualifying normal/automotive grade stuff, or using space-grade microcontrollers for in-house designs, with everything from 8-32bit, [1] and ready-made cpu boards[2] for more complex use cases. I'm sharing just 2 examples but there are hundreds, with variations on redundancy implemented in all kinds of ways too, such as in software, on multiple cores, on multiple chips, or on multiple soft-cpu cores on a single or multiple FPGAs.

[1] Example: https://www.militaryaerospace.com/computers/article/16726923...

[2] Example: https://xiphos.com/product-details/q8

[kristopolous]

The 750 is still based on a 27 year old chip and runs at half its clockspeed. The point was that spaceflight is relatively computationally modest.

[demondemidi]

Reliability is more important. Even more problematic is that many semi companies have been funneled into just a few due decades of mergers. And all of these are chasing profits which means jettisoning RAD hard mil spec devices. Up until the early 2000s intel was still making hardened versions of the 386, now they make no milspec parts.

[dogma1138]

I doubt so and if they will they’ll be abstracted to hell behind modern commodity hardware, Apollo had no bias when it comes to HDI/MMIs so astronauts could be trained on the computer interface that was possible at the time.

The reason why the controls of Dragon and Orion look the way they do is that they are no far off from modern digital cockpits of jets like the F-22 and F-35 and everyone is used to graphical interfaces and touch controls.

Having non intuitive interfaces that go against the bias astronauts and later on civilian contractors already have by using such interfaces over the past 2 decades will be detrimental to overall mission success.

The other reason for why they’ll opt to use commodity hardware is that if we are going back to space for real now you need to be able to build and deploy systems at an ever increasing pace.

We have enough powerful human safety rated hardware from aerospace and automotive there is no need to dig up relics.

And lastly you’ll be hard pressed to find people who still know how to work with such legacy hardware at scale and unless we will drastically change the curriculum of computer science degrees around the US and the world that list would only get smaller each year. We’re far more likely to see ARM and RISC-V in space than z80’s.

[johnwalkr]

I work in this space and z80, kermit and xmodem are not part of the solution. Just because this stuff is simple to the user doesn't mean it's the best suited, and there's a whole industry working on this since the Z80 days. You can buy space-qualified microcontroller boards/components with anything from a simple 8 bit microcontroller to a 64-bit, multicore, 1Ghz+ ARM cpu depending on the use case. I'm sure Z80 has been used in space, but in my time in the industry I've never heard of it.

Kermit and xmodem probably aren't what you want to use, they are actually a higher level than what is normally used and would require a big overhead, if they even worked at all with latencies that can reach 5-10s. Search for the keyword "CCSDS" to get hints about data protocols used in space.

[kristopolous]

I worked in it 20 years ago building diagnostic and networking tools ... arm was certainly around but there was also what I talked about. Things probably changed since then.

Here's kermit in space ... coincidentally in a 20 year old article. Software I wrote supported diagnosing kermit errors.

https://www.spacedaily.com/news/iss-03zq.html

I guess now I'm old.

[johnwalkr]

Thanks for the reference! Kermit could be used locally on ISS or in a lunar mission now that I think about it, but so is/could SSH, web browsers or any modern technology. But most space exploration is robotic and depends on communication to ground stations on Earth, and that is fairly standardized. Perhaps kermit will be used on the lunar surface, and that will be a simplification compared to a web browser interface. But for communication to/from Earth and Moon, there are standards in place and it would be a complication, not simplification to add such a protocol.

[kristopolous]

oh who knows ... I stopped working on that stuff in I think 2006. The big push then was over to CAN and something called AFDX which worked over ethernet. I was dealing with octal and bcd daily, mid 2000s.

I have no idea if people still use ARINC-429 or IRIG-B. Embedded RTOS was all proprietary back then for instance, like with VXWORKS. I'm sure it's not any more. I hated vxworks.

[lambda]

Yeah, I'm working on a fly by wire eVTOL project, we are using the CAN bus as our primary bus, but there are a number of off the shelf components like ADAHRS that we use that talk ARINC-429 so our FCCs will have a number of ARINC-429 interfaces.

But at least for the components we're developing, we have basically standardized on ARM, the TMS570 specifically since it offers a number of features for safety critical systems, and simplifies our tooling and safety analysis to use the same processor everywhere.

Z80 is pretty retro, and while I'm sure there may be some vendors who still use it, it's got to be getting pretty rare for new designs, between all the PowerPC, Arm, and now RISC-V processors available that allow you to use modern toolchains and so on, I'd be surprised if many people were doing new designs with the Z80

[atleta]

It seems it's going to be a new, RISC-V based chip:

[1] https://www.zdnet.com/article/nasa-has-chosen-these-cpus-to-... [2] https://www.nasa.gov/news-release/nasa-awards-next-generatio...

[monocasa]

I'm not sure if there's a RAD hard z80 variant.

They've got their own chips and protocols going back just as far, like https://en.wikipedia.org/wiki/MIL-STD-1553

[kristopolous]

The space shuttle used both z80 and 8086 until it ended in 2011. The international space station runs on among other chips, 80386SX-20s. IBM/BAE also has a few RADs based on POWER chips.

[monocasa]

Do you have a citation for that?

The Space Shuttle Avionics System top level documentation specifically calls out having "no Z80's, 8086s, 68000's, etc."

https://ntrs.nasa.gov/api/citations/19900015844/downloads/19...

[kristopolous]

Intel claims they did. https://twitter.com/intel/status/497927245672218624?lang=en although what's that word "some" doing in there...

And also, sigh, to demonstrate once again that when I worked in space it was 20 years ago, https://www.nytimes.com/2002/05/12/us/for-parts-nasa-boldly-... (https://web.archive.org/web/20230607141742/https://www.nytim...)

Knowing how 8086 timing and interrupts worked was still important for what I was doing in the early 2000s. I don't pretend to remember any of it these days.