
RTX2010 – Radiation-hardened stack machine microprocessor - lelf
http://en.wikipedia.org/wiki/RTX2010
======
lelf
Philae is controlled by 2 RTX2010 CPUs (hot red), further 8 control the
Experiments. 13 CPUs (10* RTX2010, 1* ADSP-21020, 2* 80C3x) in total. ©
[https://twitter.com/philae2014/status/427842417920712704](https://twitter.com/philae2014/status/427842417920712704)

~~~
userbinator
> 80C3x

An 8051-family microcontroller, the CPU architecture that's found almost
everywhere - including space. I wonder if they're running Forth too, as this
old discussion I found also mentions 80C32 and RTX2010 together with Forth:

[https://groups.google.com/d/topic/comp.lang.forth/7PK44n68I_...](https://groups.google.com/d/topic/comp.lang.forth/7PK44n68I_4)

~~~
analog31
The 8052AH-BASIC is better known because of a Byte Magazine article, but there
was also a commercially available 8051 variant that was mask programmed with a
built in Forth interpreter. I've never seen one.

------
samatman
The yearly Forth Day meeting is happening right now, and Chuck Moore (inventor
of Forth, designer of the RTX2010) is going to give his annual fireside chat
in a matter of hours. I'm honored to be in attendance.

So if HN has any questions, this is a good time to ask them. The hangout is
here:

[https://plus.google.com/u/0/115269917987589859757/posts](https://plus.google.com/u/0/115269917987589859757/posts)

~~~
tailrecursion
Sam, Chuck designed the Novix but the Harris RTX 2000, which is very similar,
was designed by others.

These are 16-bit chips (the Novix addressed 128 KB) that use dedicated stack
memories, that's 3 ports to memory total. The RTX puts the stacks on chip.

The nice thing about these CPUs is they can do stack, alu, and return in
parallel, interrupts are cheap, timings are predictable, and programming model
is nice if you like Forth. One disadvantage of the design is that clock rate
is limited. RAM fetch and instruction processing have to fit between pulses
meaning RAM has to be approx twice as fast as clock.

------
jng
I'm sure Mr. Moore feels vindicated that the fruits of his design work have
powered humanity's first comet landing ever.

Still, it's telling of the industry's regard for Forth that the manufacturer
itself manages to misspell the language as "Fourth" in the chip's official
product page.

~~~
cbd1984
To be fair, Moore originally wanted the language to be called "Fourth":

> The file holding the interpreter was labeled FORTH, for 4th (next)
> generation software - but the operating system restricted file names to 5
> characters.

[http://www.colorforth.com/HOPL.html](http://www.colorforth.com/HOPL.html)

It was the OS for the IBM 1130:
[http://en.wikipedia.org/wiki/IBM_1130](http://en.wikipedia.org/wiki/IBM_1130)

Because it was the cheapest computer IBM had at the time, it got used by a lot
of young pioneers in their salad days.

------
tinco
I wonder how hard it is to create a radiation hardened CPU. Is the premise
that radiation can flip bits in the on-die cache and registers? would simply
making those redundant be a solution? Or could a single flash of radiation
invalidate all memory on the device?

~~~
Sanddancer
There's all sorts of problems you have to deal with. Memory flipping is one of
the most visible, but that radiation also will damage the lattice of the
processor, making some transistors harder to flip on, and some much easier to
flip on, leading to transient glitches, etc.

Redundancy's definitely one solution, which is one reason why spacecraft tend
to have multiple processors and/or processors with redundant logic pipelines.
They also tend to use different substrates that are harder for cosmic rays to
effect, different, more expensive, casings that offer more shielding, and also
larger, older, more vetted processes. For example, this chip is uses a 1
micron process, which is a lot bigger than the process used in current cpus,
which means that there's a lot more mass in the transistors to soak the
effects of radiation, making it harder to cause damage.

~~~
Osmium
Or we can use alternative semiconductors that are more radiation-resistant.
One of many reasons why materials discovery is still very important even if
initial chips will never match the performance of silicon.

~~~
wlievens
Wouldn't work for all applications, tough, if I'm not mistaken, as you
specifically need Silicon for imaging chips (CCD/CMOS). Or is that nonsense?

~~~
Someone
Why would you need silicon for that? Even if it were the only process we use
now (which it isn't. As a simple example, Germanium-based photo diodes do
exist), materials research could conceivably produce other materials that
work, too.

There are even more exotic examples to think of. Eyes turn light into
electricity without (AFAIK) Silicon. Maybe part of that physics/chemistry can
be practically used elsewhere?

~~~
wyager
>Eyes turn light into electricity without (AFAIK) Silicon.

Correct. A photon hits a chromophore bound to an opsin protein, and flips the
chirality of the chromophore from 11-cis to all-trans, which changes the
structure of the opsin protein, which starts the cascade of activity leading
to sight. We could definitely use chemical detectors to take advantage of this
or a similar process.

------
jacquesm
Hah, an old friend. A company I worked with had a Novix in 1986/1987 for
prototyping purposes (early days number plate recognition system). Before we
got it we had to sign an unreasonable amount of paper. Rumor had it this is
the chip powering the Tomahawk cruisemissile.

~~~
abecedarius
Brought a smile to my face too: I had a summer job in 1986 at FORTH, Inc., and
spent some quality time with my officemate's cmForth manual. (cmForth was
Chuck Moore's new Forth dialect for the Novix. IIRC the manual said the
multiply-step instruction didn't quite work and gave a software workaround.)

------
jesrui
Another microprocessor able to execute Forth natively is the b16, from one of
the original authors of Gforth.

[http://bernd-paysan.de/b16.html](http://bernd-paysan.de/b16.html)

~~~
ryanmk
There's also GreenArrays GA144, which has 144 forth machines on a single
microprocessor.

[http://www.greenarraychips.com/](http://www.greenarraychips.com/)

------
mud_dauber
How cool - I joined Harris after grad school expressly to work on RTX
architecture issues. (Previously I was a Forth developer.)

Nice to see this neat-but-underappreciated architecture in the news.

~~~
naland
>Nice to see this neat-but-underappreciated architecture in the news.

It's already appreciated. Let me recall here the 'scientist' character (A&B
Srugatsky) who explains the World as a huge inertial mass to the good or evil
in the same.

Tertium non datur it is a principle of our mind sometimes used in computers.

~~~
naland
edit: Strugatsky. hi ±HN.

~~~
abecedarius
I believe the downvotes came from not seeing any relevance to your comment --
I don't see it myself.

------
lucaspiller
Tech specs are available on the manufacturer's site:

[http://www.intersil.com/en/products/space-and-harsh-
environm...](http://www.intersil.com/en/products/space-and-harsh-
environment/rad-hard-digital/rh-microprocessors-and-peripherals/HS-
RTX2010RH.html#0.html)

------
imrehg
Listed but unfortunately not stocked:
[http://www.mouser.tw/Search/Refine.aspx?Keyword=RTX2010](http://www.mouser.tw/Search/Refine.aspx?Keyword=RTX2010)

~~~
kens
I looked on Alibaba and Shenzhen suppliers have the HS9-RTX-2010-RH for sale
at 10 cents a chip, able to supply up to 100,000 chips per month.

How do they do this? They're lying. Various Alibaba vendors list literally
every part number they can find as something they are selling. If someone
wants it, then they see if they can actually get it.

In any case, the real price for the RX2010 was between $1000 and $10,000
according to this thread I found from 1999:
[http://www.strangegizmo.com/forth/MISC/msg01281.html](http://www.strangegizmo.com/forth/MISC/msg01281.html)

~~~
mud_dauber
Of course they are. The last place I'd go for reputable semiconductor
suppliers is Alibaba. The LAST.

------
SixSigma
A very closely related processor, the RTX2000, is described in detail in
Koopman's book "Stack Computers: the new wave"

[http://users.ece.cmu.edu/~koopman/stack_computers/index.html](http://users.ece.cmu.edu/~koopman/stack_computers/index.html)

The RTX2010 has had its own wikipedia entry too since 2008 :
[http://en.wikipedia.org/wiki/RTX2010](http://en.wikipedia.org/wiki/RTX2010)

------
programmer_dude
Can someone point to resources comparing stack machines and register based
machines? The RTX2010 technical documentation talks about all the advantages
of a stack machine but doesn't say anything about its shortcomings.

~~~
wlievens
Optimal register allocation is an NP-complete problem. By doing away with it,
you don't need to allocate registers.

How that compares on a practical level, I have no idea. But it's one of the
reasons the JVM has a stack-based model and no registers: it makes writing
compilers for JVM byte code a lot easier.

~~~
CHY872
This isn't quite right - we don't in general really care whether we're
allocating optimally (for example, if we have 16 registers we don't care if we
can potentially allocate to 10), and heuristic based approaches are
practically very useful (and cheap).

In terms of compiler writing, if you wanted to write any optimisations you'd
probably want to manipulate 3-address code internally, if only because the
data flow based analyses would be made easier (and then you would emit stack
code in the last step).

This might be a reason why the JVM designers decided to use a stack machine,
but I doubt it's an important one - they'd easily be able to get ahold of a
few decent compiler writers if they needed to.

~~~
wlievens
I don't doubt the JVM designers have good compiler writers. I rather think
that they wanted the bytecode to be accessible to write for _other_ compiler
writers, such as the team that implemented JSP servlets a century ago, but
also perhaps with a future vision for the alternative JVM languages.

