Ask Chuck Moore About 25X, Forth And So On

Chuck Moore is, among other things, a chip designer. His latest design, the 25x, is based on a 5x5 array of X18 microprocessor cores, and could provide 60,000 MIPS with a production cost of about one dollar. And Moore has the chops to back that up: he's been designing tiny, efficient processors for many years. He's also the inventor of the programming language Forth, which has evolved from a miniscule but radically fast language "difficult for a human to read" (according to The Secret Guide) to the even more radical colorForth. How radical? Try "includes own operating system; has own 27-key Dvorak keyboard layout; meaningful color syntax." How's that for starters? Ask below your questions for Chuck about processors and programming (ask all you'd like, but one per post, please) We'll pass the best ones on to him, answers soon to follow.

5x5 grid of procs

[Lord Kestrel]

What kind of signalling method are you for inter-proccesor communication?

And what led you to design/implement this array?

Forth as intermediate language

[Ed Avis]

Many high-level languages compile into C code, which is then compiled with gcc or whatever. Do any use Forth instead? I understand Forth is a stack-based language: doesn't that present problems when compiling for CPUs that mostly work using registers?

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Direction of Forth/25x

[rho]

Do you have a direction in mind as to where Forth/colorForth and the 25x could go? e.g. do you see them in handhelds, set-top boxes, etc?

Market Niche

[kaladorn]

What market niche will the new grid-array processor be targeted at? 60 BOPS is a fair value for a buck. But is the power consumption ridiculous? Or would this be suitable for deployment in various mobile applications? Or is the only way to get this high of projected performance by clocking the chip like a six year old on chocolate frosted sugar bombs?

And an aside:
My ignorance of Forth might be showing (one of the few I haven't had kicked into me over the years) - but wouldn't "meaningful colour syntax" represent quite a nasty disadvantage for those who are either entirely or partially (red-green) colour blind?

And speaking of Dvorak... anyone know where I can get an ergonomic, full sized, keyboard with a Dvorak key layout. I can probably remap the keys on the existing MS keyboard, but the idea of switching the keycaps is nasty. It'd be better to have a keyboard that sent the right scancodes.

revolutionary

[rnd()]

Put on your Thomas Kuhn hat for a moment and tell us:

What is the most revlutionary (i.e., it is scoffed at by those in control/power) idea in the software industry today? Explain how this idea will eventually win out and revolutionize software as we know it.

uh, forth post?

[alienmole]

Sorry, couldn't resist.

Forth is a very cool language: I first used it running on an Apple ][ a couple of decades ago, to write programs to control lasers for laser shows at a planetarium. The combination of interactiveness and performance was great - it allowed details of a show to be reliably tweaked right before and even during a show. This was one of those situations where the tool really made a difference to the end result. Other languages available on the Apple at the time couldn't really compete.

I don't have a question for Chuck, but I'll come back when I think of one.

What's the next Big Computational Hurdle?

[DG]

Now that sub-$1k computers are running in the GHz range, it seems that all the computational tasks on a common desktop system are not processor-bound.

3D, rendered-on-the-fly games get well over 30 frames per second at insanely high resolutions and levels of detail. The most bloated and poorly-written office software scrolls though huge documents and recalculates massive spreadsheets in a snap. Compiling the Linux kernel can be done in less than 5 minutes. And so on.

It seems that the limiting speed of modern computers is off the processor, in IO.

What then, do you forsee coming down the pike that requires more processor power than we have today? What's the underlying goal you intend to solve with your work?

Where is forth going?

[JanneM]

I learned forth early on in my programming career; it was very memory and CPU efficient, something that was important on early microcomputers. It was also a great deal of fun (though far less fun to try and understand what you wrote a week earlier...). Today, even small, cheap microcontrollers are able to run fairly sophisticated programs, and it is far easier to cross-compile stuff on a 'big' machine and just drop the compiled code onto the development board.

Forth has (in my eyes) always been about small and efficient. Today, though, embedded apps are more likely to be written in C than in forth, and the "OS as part to the language" thing isn't as compelling today as it was in the eighties. Where is forth being used today, and where do you see it going in the future?

/Janne

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Programming languages...

[Midnight Ryder]

This one would probably require a bit more time to answer than you probably have available, but a quick rundown would be cool: Where do you see programming languages headed -vs- where do you think they SHOULD be headed? Java, C#, and some of the other 'newer' languages seem to be a far cry from Fourth, but are languages headed (in your opinion) in the proper direction?

Newbie / Future MISC Chip Designers

[Anonymous Coward]

Chuck,

I've read everything on your site & also Jeff Fox Ultratechnology.com site about your Minimal Instruction Set Chips, their design, performance etc.

What advice and tools would you recommend to anyone today starting out and wanting to follow and build upon the path that you've set out?

Very Interested?

What is Forth?

[Innominandum]

Someone on Slashdot has recommended Forth to me as "perfect middle ground between ASM and C." I have looked at the FAQs and could not find a quick-and-dirty overview of the language.

I am looking for the simplicity, control, and elegance of ASM. But I also would like to enjoy some degree of abstraction and features that reduce the drudgery of programming. I have looked at HLA and Terse but they are platform-dependent, unless I write my own compiler. Do you think Forth meets these criteria?

Another thing. Just from peeking at the FAQ I see Forth uses postfix expressions (among other things), which seems a little dated. I assume this was implemented for compiling on resource-constrained machines? Do you plan on giving Forth a minor face-lift?

Quick question

[jd]

I have often conjectured that multi-threaded processors (ie: processors that can store multiple sets of internal states, and switch between them) could be useful, as the bottleneck moves from the processor core to communications and dragging stuff out of memory.

(If you could microcode the "instruction set", all the better. A parallel processor array can become an entire Object Oriented program, with each instance stored as a "thread" on a given processor. You could then run a program without ever touching main memory at all.)

I'm sure there are neater solutions, though, to the problems of how to make a parallel array useful, have it communicate efficiently, and yet not die from boredom with a hundred wait-states until RAM catches up.

What approach did you take, to solve these problems, and how do you see that approach changing as your parallel system & Forth language evolve?

The direction of 25x Microcomputer...

[Midnight Ryder]

The 25x concept looks like it could really a damned interesting idea. But one of the questions in my mind is where you want to head with it? Is this something that is to be used for very specialized research and scientiffic applications, or is this something that you envision for a general 'desktop' computer for normal people eventually?

Secondly, if you are considering the 25x for a desktop machine that would be accessable by people that aren't full-time geeks, what about software? Forth is a lost development art for many people (It's probably been 10 years since I even looked at any Fourh code) and porting current C and C++ application would be impossible - or would it? Is there a potential way to minimize the 'pain' of completely re-writing a C++ app to colorForth for the 25x machines, which could help to speed adoption of a platform?

What is Forth

[mcelrath]

This is going to be a stupid question...but one I suspect many will have.

What is Forth? Why is it useful? How fast is it in terms of useful computations? X MIPS, when comparing miniscule Forth instructions to CISC Intel instructions isn't really a good comparison. So how many *useful* computations can it perform compared to modern processors? What has it been used for in the "real world"?

I recall a company creating a transputer -- basically an array of FPGA's, all doing 4-bit add operations, and claimed X thousand MIPS, where X is large. How are Forth machines different?

Questions for Chuck.

[Crusty Oldman]

I love Forth, always have. From the first hand-entered FIG listings to the excellent Win32Forth, I've known this is the "right" computer language. So why doesn't the rest of the world see what is so abundantly clear? Is it because they can't make the small mental leap to RPN?

And why isn't Forth used more as a platform? Is it speed, security, advertising, what? I've never understood why the Forth community will take an excellent implementation right up to the point of being useful, then leave it without developing any applications. I can see an efficient, user configurable web cruiser built on any one of a number of Forths. But nobody has done it. Ditto for httpd servers. Why?

And to the rest of the world, please stop parroting the old line about Forth being hard to read. It isn't. You can pick up most of what you need to know in an afternoon, then begin to enjoy some very elegantly stated code.

Information theory

[BillyGoatThree]

* 5 x 5 array of cores: 60,000 Mips

...

* Max power 500 mW @ 1.8 V, with 25 computers running

500 milliWatts is .5 J/s. Divided by 60,000 million instructions/second implies that this can execute 1 instruction while consuming only 8.3e-6 Joules of energy. What I'd like to know: Pretending for a moment that the instruction was simply to flip a single bit, how close does this come to the absolute limit dictated by Information Theory?

Re:Ahem

[Spotless Tiger]

(Which, for the sake of people reading the above and going 'huh'? actually reads:

"Forth is well known for storing all keywords as three letters and the length of the name. Why was this design decision held onto even after memory became cheap enough for space not to be an issue"

Trust me, Moore will understand it without the need for translation...)

Massively Parrallel Computing

[PureFiction]

The 25X system reminded me of IBM's Blue Gene computer, where a large number of inexpensive CPU cores are placed on a single chip.

The biggest problem in dealing with a large number of small cores lies in the programming. I.e. how do you design and code a program that can utilize a thousand cores efficiently for some kind of operation? This goes beyond multi-threading into an entirely different kind of program organization and execution.

Do you see Forth (or future extensions to Forth) as a solution to this kind of problem? Does 25X dream of scaling to the magnitude that IBM envisions for Blue Gene? Do you think massively parrallel computing with inexpensive, expendable cores clustered on cheap die's will hit the desktop or power-user market, or forver be constrained to research...

Object-Oriented Programming

[nate37]

Chuck,
What are your views on Object-Oriented programming and how it would relate to forth?

Re:Forth as intermediate language

[William Tanksley]

You reversed the two -- stack based architectures are simpler to optimise and allocate for than register based ones.

In a register-based architecture, you don't know which register is going to be used next, and which ones are seldom used; in a stack, you know that stuff near the top is coming sooner than stuff near the bottom. Because all of the data is ordered in terms of urgency, a caching system can make very intelligent decisions.

This is even more powerful when the programmer (not the compiler) is the one who arranged the data in order on the stack -- the programmer has an optimiser in his head which by FAR defeats all currently possible software optimisers.

-Billy

Postscript ~= type checked Forth...

[Svartalf]

Someone wrote a Postscript program around 1987-88 that allowed the interpreter to compile Forth words straight from the command interpreter. It was all of two to three 8.5 x 11 pages of 12 point text, if memory serves.

Marginalizing of the blind

[Medievalist]

When I built my first Internet node, the web did not yet exist, and one of the amazing things about the Internet was how friendly it was to the blind.
Now, with some computer experts estimating that over 50% of the Internet is incomprehensible to braille interfaces, and most computer operating systems devolving to caveman interfaces ("point at the pretty pictures and grunt") we seem to be ready to take the next step - disenfranchising the merely color-blind.
I realize that colorforth is not inherently discriminatory, in that there are a great many other languages that can be used to do the same work. The web is also not inherently discriminatory, because it does not force site designers to design pages as stupidly as, for example, Hewlett-Packard.
Would you care to comment on the situation, speaking as a tool designer? How would you feel if a talented programmer were unable to get a job due to a requirement for colored sight?
--Charlie

FFP, Combinator Calculus and Parallel Forth

[Baldrson]

In his 1977 Turing Lecture, John Backus challenged computists to break free of what he called "the von Neumann bottleneck". One of the offshoots of that challenge was work on massive parallelism based on combinator calculus [nec.com], a branch of mathematics that is far closer to Forth's formalism than parameter list systems (which are more or less lambda calculus derivatives). The prolific Forth afficionado Philip Koopman did some work on combinator reduction related to Forth but seems not to have followed through with implementations that realize the potential for massive parallelism that were pursued in the early 1980s by adherents of Backus's Formal Functional Programming paradigm. Given recent advances in hierarchical grammar compression algorithms, such as SEQUITUR [rutgers.edu], that are one step away from producing combinator programs as their output, and your own statements that Forth programming consists largely of compressing idiomatic sequences, it seems Backus's original challenge to create massively parallel Formal Functional Programming machines in hardware are near realization with your new chips -- lacking only some mapping of the early work on combinator reduction machines. It is almost certainly the case you are aware of the relationship between combinator reduction machines and Forth machines -- and of Backus's challenge. What have you been doing toward the end of unifying these two branches of endeavor so that the software engineering advantages sought by Backus are actualized by Forth machines of your recent designs?