Let us first start by dividing the types of extreme condition into several categories, and examine each category independently.
Extreme conditions can involve one (or more) of the following factors: Extreme radiation, extreme temperature values, extreme temperature variation, extreme acceleration, extreme speed and extreme reliability.
Extreme Radiation: This is becoming an increasing problem, not just for NASA, but for the technical industry as a whole. As computers become faster, they need to operate over narrower voltage ranges, to keep the heat down. (It's not much use if the computer cooks itself.) But, in the process, you need less and less outside interference to flip the state of any of the hundreds of millions of transistors.
How much energy is required to interfere with a computer chip? Well, if you have a 3.3v line, operating at 2 GHz, the energy in a single "state" is 3.3/200000000 of a watt, which is absolutely insignificant. A good, solid thwack by a cosmic ray could easily produce energies much higher than that, at aircraft altitudes, and are probably a measurable hazard even on the ground.
(The air is much more hazardous, as the atmosphere absorbs many of the high-energy particles, long before they reach the surface. Also, your house is probably a bit sturdier than an ultra-light airframe.)
Ok, so radiation is important to users of mobile computers in the air, and (as speeds increase) to computer users in general. It's absolutely critical, though, to all those computers the aircraft uses to navigate and fly. Spacecraft (probes, the shuttle, the space-station, sattelites, etc) get absolutely drenched in intense radiation, though. If the computers in the Space Shuttle get fried by radiation, the pilot can't simply order a fresh system over the phone.
For the avionics and space industries, then, there are entirely seperate, distinct computer industries, designed to serve specifically those kinds of needs. The components have much higher radiation tolerences (>100 Krads, in many cases, and a few >200 Krads), but the penalty is often much slower, and MUCH more expensive, components. These things don't come cheap.
There are three techniques for handling radiation, and different companies use a different mix of them.
The techniques are: Hardening of existing components, Building your own components, and Buildng tougher casing.
Hardening of existing components often involves re-arranging the components, adding error-checking and other wonderful stuff of this kind. The "Top Of The Line" components in this field are things like the Radiation Hardened Pentium Classic and the Radiation Hardened Sparc V7. Definitely not your latest-and-greatest! NASA has a basic primer to Radiation Hardening. Materials Science and Engineering, at Virginia Tech offer a more comprehensive tutorial on Radiation Hardening
Building your own components can be fun. And it's not that expensive! The technique used is called a "Sea of Gates". The system is essentially a massive array of radiation-hardened gates, with no interconnects. The customer then specifies a connection mask, which can then be retro-fitted to the Sea of Gates, producing a hybrid Custom / Mass Produced component. It's not as fast as a "pure" custom-built chip, but if you don't have a few billion to spend, then it's a good alternative.
Building toughened casing seems to be a relatively new field. The idea here is to abandon hardening the silicon, and to harden the case instead, making it opaque to high-energy particles. Because it is the case that is hardened, this technique can be used on any modern electrical component, regardless of speed.
Who makes these "radiation-hardened" systems, anyway? Well, here are a few companies that do:
A glance at these will show that many also produce components for the military. Well, duh! They're the ones who have funded most space research, have put most of the hardware in space, and are the only ones rich enough to afford to buy the rockets needed to get there. (They're also about the only ones licenced to even have that kind of rocket power.)
The list is not meant to be exhaustive, but rather a good selection of the sorts of things people produce. By glancing through the data sheets, you can see the sorts of conditions these devices are designed to handle. And it's not pretty.
Ok, so let's get back to the initial question. Why do people like NASA use 60's and 70's technology? Partly, because it's already tried and tested under the hostile environment of space. NASA knows what to expect. Partly, it's because the chips are much slower, and the transistors are much larger. This means that you need a significantly more powerful blast of radiation to mangle things. Lastly, it's because these chips are cheap - in price and in overhead. An 8086 doesn't have any space used up on MMX instructions, for example.
Price? Doesn't NASA have enough money? Well, no, they don't. Their resources are very limited, and shrink with each budget, both in absolute and real terms. A rad-hardened Pentium is likely to cost more than the rest of the satellite's systems put together. If you don't need the speed, you don't need the price-tag.
(That NASA is actually shopping on e-bay only goes to show just how severe their budget has become. There are other processors out there that'll work for what they want, and they know that. If they have to worry about margins that much, then you are looking at an organization that hasn't the money to safely launch a bottle rocket, never mind a Titan.)
For extreme temperatures, many of the same companies cover that ground as well. However, a search also turned up Lake Shore Cryotronics, as a company covers specifically high-temperature electronics and microelectronics. Another company that deals with temperature is Mikro Elektronik gmbh, a German company. (And I thought it sounded Australian! :)
Extreme motherboard designs (I don't have a URL to hand) can handle up to 20G, and some fairly vicious shocks. This would be good for, say, the volunteer lifeboat services, where tiny boats are skillfully navigated through violent storms, in efforts to rescue survivors from shipwrecks or aircraft crashes.
You can buy components for protecting entire systems from severe shocks and stress (one such system is sold by CSA Engineering for protecting satellites from the stresses of rocket launch.
What sorts of OS do people run on computers like these?
Well, probably something light-weight and real-time. You can't afford to wait whilst the disk is syncing, if you must give a correct response in the next three tenths of a second, to survive. You also can't afford anything memory-hungry (you won't be able to add that much memory), cycle-hungry (you can't afford the power requirements) or disk-hungry (a spinning hard-drive ain't gonna survive the North Sea, or a rocket launch).
This reduces your choice, considerably. In fact, you basically have a choice of the following:
- QNX - One of the "classic" real-time OS'. It's popular, it's effective, and it does the job.
- VxWorks - a Unix derivative, specifically designed for scientific and other extreme conditions. It's expensive, as is the hardware required, but it's generally considered "the best".
- Roadrunner/Pk - about the most basic RTOS you can get, but if you are tight on RAM, it's a good one to go with.
- Exopc - an experimental high-performance OS from MIT. I'm not sure if it's strictly RTOS, but it does have low latency and a design that offers a lot of potential.
Temperatures: Most modern electronic components come in one of two temperature ranges: -40 to +65, and -20 to +65. (All temperatures are in celcius.) This is fine, for most desktop PCs, but what if you were in the middle of the Antarctic? If your components go out of range, above or below, they can be damaged or destroyed.
Again, we look to the suppliers of the military. Military standards are much more exacting than those the rest of us get to put up with, and the temperature ranges are much more severe.
Capacitors and Connectors, for example, sell military-grade components. The typical range rockets to -55 to +125. You can now talk about computers that can be used to boil water, and remain operational, or be used where CO2 falls like snow. Other companies selling extreme temperature hardware are Vishay and Microcapacitors.
Ok, so when would you need such components? Let's take a look at some examples. Ships in the North Sea are often in conditions so cold that the sea spray will freeze solid on impact. The Arctic and Antarctic visitor is likely to experience conditions many times colder yet. As for any future manned mission to Mars.... That polar ice cap is still believed to be frozen CO2, so anyone going is likely to need to wrap up warm.
That's a significant number of groups that experience extreme low temperatures. What about high temperatures? Well, I imagine most vulcanologists can name situations where high temperatures might be an issue. Nor would I want to run a standard air-cooled PC in Death Valley. Firemen, using sensors to detect trapped people, need electronics that won't fry, if the people aren't to fry too.
All in all, surviving high temperatures is an issue for a lot of people. And, as I said, most of the components designed for that kind of work are designed for the military.
What about high temperature variations? Materials expand and contract with temperature, and if the variability is too great, the material will simply fall apart. Components that have materials with different thermal expansion properties have a worse time. They can bend, break, and then disintegrate. Not good.
I've not found components designed for high variability, but I'm going to assume that the military gradings take this into consideration.
I'll deal with extreme speed and extreme reliability quickly. (Hmmm!) The colder you make an electronic component, the faster you can make it run. This is why supercomputers are invariably super-cooled. And this gets back to needing components with high temperature tolerance. The greater the tolerance range, the colder you can get the system, and the faster the system will then run.
The current "land-speed" record for a Pentium IV is about 3.66 GHz, using a 2.0 GHz P4 as the starting point. The current top-of-the-line P4's should scale even better.
The drawback of overclocking like this is that nobody really knows the impact on the components. Terms like "electron migration" are bandied around, but nobody has really studied this in depth. What is certain, though, is that the effects will be dependent on the amount of cooling versus the amount of overclocking.
Extreme reliability: This is something that older components (again!) do better, because there are fewer parts to go wrong, and it requires a greater cause to produce such a fault.
Typically, components have what is called a "Mean Time Between Failures". And, again, your computer is likely to be made up of parts with abysmal MTBF's, and the jet fighters are likely to have parts that'll likely survive into the next millenium after the one that comes after we invent Star Trek transporters.
Actually, this is the most realistic part of the old Buck Rodgers stories. It is entirely believable that the components in a Space Shuttle could be of a quality such that the MTBF exceeds 500 years. And I would be very surprised if there were not military systems in use today with MTBFs in that kind of order.
"Domestic" uses for such systems would include emergency medical equiptment ("Oops! The Life Support blew a fuse. I'll be back in an hour!") and systems for other comparitively critical systems, where a single failure in the operational lifetime is one failure too many.
This is why many computers, programs, etc, have large disclaimers, prohibiting any use in nuclear reactors, life support systems, etc. It's because the MTBF is just too low to take real risks with. But your home banking & recipe book isn't worth as much (to them), and customers don't care enough about the MTBF to warrant spending the extra bucks in building a more robust system.
(If you're going to replace your PC every 3-4 years, do you really NEED every component guaranteed to last 30-40 years, under maximum load? Or will something that could well burn out in 4 years be just as good?)