Re: Wire Computing? A Theory
- --- In firstname.lastname@example.org, Martin McKee wrote:
>Wow, that must've been the quickest response I've ever lived to witness on this page. Seriously, within 6 hours! But anyway, that's exactly what I'm getting at. It would be like some sort of "BEAMborg". My entire point is that BEAM never sleeps, but the microcontroller can, and it's preferable that it does. I mean, you have reflex responses built right into the motor driver circuitry, that way the extra circuits have almost no impact whatsoever on power consumption, but still work the robot toward its goal while the processor is idle. Basically free mileage. And I still maintain that it makes programming the robot somewhat simpler, since even a simple physical network can work to dynamically resolve a command, allowing for "low-resolution" programs, giving the programmer quite a bit of slack. I think it would be just a bit easier to understand and more user-friendly. And while the computer may have plenty more resources to offer, I like to leave as much room as I can for later.
> With some of the new ultra-low power microcontrollers, I do wonder about
> the actual power saving potential of using discrete circuitry. In sleep,
> even with an asynchronous timer running, microcontrollers are getting down
> into the sub micro-amp range. Even running thus, they can be woken up with
> a number of triggers: edge or level sensitive, timer overflow, analog
> comparator, and, in some rare cases, masked analog to digital comparisons.
> It is now much more power efficient to run a microcontroller at full speed
> to do what ever computation is required and then sleep a majority of the
> time ( assuming, of course, there is nothing like a slow serial bus that
> keeps the micro awake ). What does still seem to be a major advantage to
> BEAM circuitry is the ability to react immediately to change in stimulus.
> It makes for an exceptionally tight control loop which is difficult to
> match even with dedicated processors. So, it still seems the best option
> to build a highly capable, efficient and adaptable robot is going to
> involve some combination of "analog" ( BEAM-like ) and "digital" (
> processor-based ) control system.
> So much to discover, so little time,
> Martin Jay McKee
- Yeah, the usability bit is a primary focus of mine. Just for fun, really, I've taken an approach at a very traditional style, basically using a set of counters in place of an actual processing unit. At it's simplest, it lacks the hardware to perform Boolean logic operations outside of 1's and 2s complement, but these can still be used to simulate logic functions in a few cycles. It can also simulate bit shifting easily enough by multiplying or dividing by 2. It also places quotients and remainders into different registers for easy handling of remainders. Not to mention floating point math isn't difficult, either. It could even perform <, =, > comparisons between values. As a matter of fact, I can't really say that any electronic computer has ever been built in this fashion. I'm pretty much basing the design entirely on DigiComp2, a mechanical 4-bit binary computer distributed as an educational toy from 1968-1976.
Yes, the 1-bit processor array concept is in fact cellular automata, which is why I refer to each unit as a "cell". I don't entirely understand bandwidth, yet. But the idea doesn't really focus on that. It regards robustness of the system, as well as massive parallel processing without most of the usability problems. I would also think it much more flexible, because a key construct is that each cell can alter its connectivity with its neighbors. It would take several orders of magnitude more component failures to trash the system than your traditional hardware, it could also be incredibly fault tolerant, and I'm thinking on the lines that the entire system would be programmed as a whole, so that determining how each cell should connect can be left up to the OS shell. Also, even if bandwidth restricts how quickly information is processed, another perk of the idea is that a very large amount of data could be processed at once.
On a side note, I once came up with an idea for a machine that was mostly electronic, but stored data temporarily as photon states(like, particle for 0 and wave for 1), and would be able to take advantage of the fact that photons, being 4-dimensional objects, can move in more directions than we can perceive, and thus allow the machine to literally do everything at once. What I mean is that each new cycle would take place in the same time frame as the last cycle, so that it could register an infinite amount of data in about a billionth of a second or so. It would only ever have to go forward in time if it needed to write a result back to main memory or update I/O, because the way it works, the events that occurred in previous steps literally would have never happened, and so the electronic memory wouldn't be able to remember such a result, and the outside world could only observe the final state of the program, if there was one. Fundamentally it is a photon based delay line with a negative delay. As in, instead of the delay propagating forward in time, it "rewinds" time slightly. So the potential would be literally instant computation, a stack of infinite size could be fed into the computer and processed in less than a billionth of a second, and an entire program run could be accomplished in the same amount of time. Branches and subroutines would be included. Only writing data back to memory or porting to the I/Os would really take any time at all. Only the program's final result could be observed from outside, as each step in between would never have happened in our timeline. Also, the program counter would have to be photon based, somehow, since if it was electronic, it wouldn't be able to remember what program line to go to next after time was rewritten again. The only thing I can see being interpreted as dangerous with this is that it does, indeed, rewrite time. But it only rewrites about a billionth of a second each time, and it doesn't effect outside events whatsoever. It has absolutely no way to affect reality.
> For myself, life is catching up with me. Come Monday, I'll be starting a
> new degree ( one not even tangentially related to my first ), so I've been
> rushing around trying to get all that in order -- no time for seriously
> thinking about robotics at all.
> I've only got a minute or two now, but, some few comments. The massively
> parallel 1-bit processors sounds a bit like a cellular atomaton type
> system. I remember having see once ( but can I find it now? of course not!
> ) a computer system that was being developed in that vein, compiler and
> all. There is certainly potential for quite a bit of performance, but for
> maximum performance, the bottleneck is often memory bandwidth, and not,
> strictly, computational. A large number of processors with a handful of
> neighbors and a 1-bit interconnect is not going to help in that line.
> To be honest, much of the architecture design lately has been targeted at
> increasing performance ( adding parallel instruction sets, vectorizability,
> hyperthreads, etc. ) but because of memory access issues and programming
> concurrency issues, simple small instructions and a minimal set of fully
> atomic instructions has seemed to have the best balance of usability and
> performance. No one has really been able to demonstrate an architecture
> that is both highly performant and efficient in the face of concurrency (
> and many parallel computational units ) while remaining easy to program. I
> think what can be said about "traditional" architectures, is that they are
> easy to understand and they work "well enough."
> Back to work...
> Martin Jay McKee