A Bendy RISC-V Processor
spectrum.ieee.org
spectrum.ieee.org
Eg. rather than having every pixel in your flexible screen be flexible, you make each pixel rigid and have the joints between pixels flexible.
In this case, this design is based on SERV, which uses ~2100 gate equivalents, which in a recent tech node would be 40 um^2. That means you could fit a 10x10 grid of these in a single pixel on an iphone screen.
I really can't think of a use case where a region 1/100th of an iphone screen pixel being rigid would be a problem.
1) How would wiring to you processor work?
2) How many flexible compute applications are currently using just really small processors?
3) Given that Pragmatic has raised a lot of money, what was it in their use case that the investors thought would make a better product?
4) Besides flexibility, are there other requirements in this product space?
5) Given that you've just imagined a product with a flexible screen but solid pixels, does this exist on the market? Are there flexible screens on the market? How do those screens choose to implement flex versus the idea you have proposed? What factors might make their choices better (or worse) than the idea you proposed?
I'm not being critical here, I think you start with an excellent starter question which is "Would the requirements be satisfied by sufficiently small electronics such that [the] lack of flexibility [in the electronics] doesn't matter?"
The trick then is to see if you can see how other people who invested time and money in answering either that, or a closely adjacent, question answered it. When you do that you'll get to see what they thought the overall requirements were vs the technology they picked, and perhaps it might inform if the Pragmatic solution would be a better fit or the 'tiny electronics' solution would be a better fit.
I'll be the first to admit that I'm 'weird' in that I really do enjoy going down these sort of engineering optimization rabbit holes to develop a better understanding of what problems various proposed solutions are trying to solve.
My (relatively limited) experience is that this is what really makes wearable projects obnoxious.
Even if you have a chip with a tiny footprint, you either put it on a breakout board that isn't tiny or you spend twenty hours soldering nearly microscopic bits of magnet wire to it. It's the same for the piles of passive components and peripherals that every project requires, the voltage regulators and smoothing capacitors and power transistors and stuff: You either attach everything to a big PCB or you're faced with a spaghetti nightmare of point-to-point wiring that makes "normal" dead-bug circuitry, the kind you might find embedded in a block of resin for aesthetic points, look like a walk in the park.
Flexible processors don't necessarily solve that problem, but they definitely demonstrate that flexible circuits in general are advancing in useful ways, better signal quality and longer runs and better process yield. The bigger these things get the better they are for replacing that mess of integration spaghetti that I always see DIY wearable projects suffering from.
(I think that industrial wearables typically solve this by concentrating everything complicated down to a rigid brain-box, c.f. smart-watches or those heated jackets that have a socket for a power tool battery in the pocket.)
A real chip would only need two or three contacts to vastly outperform thing demonstrated here. These would probably not be soldered, they would ideally be bonded directly to the chip.
Imagine a near-microscopic 4-ball BGA on a bit of flexible PCB, except the PCB material can flex in multiple axes simultaneously.
[1] "Die Attach Comes to PCBs" --- https://www.eeweb.com/die-attach-comes-to-pcbs/
OT, but I've been wondering how one might teach this young. Perhaps LLM-generated business case studies? Other thoughts? Part of the context is generative storytelling might permit intensively overlaying implicit curriculum on to existing learning objectives (eg, it's a chemistry problem, but chosen to also scaffold biology and illustrate supply chains).
Sure, there's a modulus gap to be interfaced, but flexible circuits have been worked on forever.
The whole point is of this tech is that the transistors themselves are flexible.
But since the transistors they end up with are orders of magnitude worse than what the microprocessor age started with, to me this just shows that this tech is not anywhere close to practical application.
My original point was that dismissing the technology out of hand because you imagine you could solve the same problem with tiny ICs is probably premature. Dismissing any technology coming to market because you think it doesn't solve any problem is usually a bad idea because it takes non-zero effort and resources to bring anything to market. As a result, if you imagine what something is irrelevant because there are other proven solutions, then take that as a signal to say "Hmmm, what am I missing here?"
> But since the transistors they end up with are orders of > magnitude worse than what the microprocessor age started > with, to me this just shows that this tech is not anywhere > close to practical application.
This doesn't really track though does it? The "first" microprocessor, the 4004 ran at 750kHz max. Most of the challenge here appears to be heat dissipation as plastic melts at a much lower temperature than silicon, but the chemistry is still interesting.
I completely agree that this isn't going to displace servers in the data center any time soon, but I can imagine applications for an all (or nearly all) plastic computer on a flexible plastic substrate.
[1] Their IP (not the reader though) lives on at https://www.e-pi.com/
The 4004 wasn't useful to power a general-purpose computer as we think of one today, it was made for a 4 function calculator and it's hard to find many examples of it being used in other systems online. It took another 10 years of Moore's Law for the ingredients to come together and microprocessor-powered desktop computers to achieve critical mass.
Look at Table 2 in the (awful, IMO) Nature article. This thing is 10x slower than even a 4004.
> Dismissing any technology coming to market because you think it doesn't solve any problem is usually a bad idea because it takes non-zero effort and resources to bring anything to market. As a result, if you imagine what something is irrelevant because there are other proven solutions, then take that as a signal to say "Hmmm, what am I missing here?"
100%!
But is there reason to think Moore's Law is happening here?
Or did these researchers just print some minimum viable transistors on kapton?
Ie. IPC will be 30x worse than a microcontroller core, and 200x worse than a desktop PC core.
(couldn't find exact numbers)
It's pretty incredible considering the 6502 was already considered tiny when it was released with just ~4500 gates vs the 6500 in the 8085 and the 8500 in the z80.
So realistically, if you need fully custom digital logic, you'd buy LFE5U-12 instead and program that.
So that's $16 FPGA from widely available distributors (like Digikey) who likely can afford 1 or 2 day shipping.
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Custom chip design for a flex-circuit is interesting, but only if you have substantial analog parts that cannot be easily implemented by an FPGA.
They usually care about at least one of - size, power, cost.
The main obstacle that has prevented this until now is that in all high-bandgap semiconductors it is easy to make only transistors of a single polarity, not transistors with both polarities, as required for CMOS logic. For high circuit densities it would be difficult to replace the CMOS logic, because all alternatives have higher idle power consumption.
I think this flexible CPU tech is interesting. If it's possible to build an ADC onto it and monitor flexible sensors, that would open up one kind of possibility, and probably an advantage over chip-on-flex solutions. I'm sure there are many more interesting uses for this.
It's impressive that a CPU can be implemented with this tech, but interesting things can be done with far fewer gates.
We're talking about a 3mm bend radius here, so there's a few orders of magnitude to work with.
Bonding wires to the thing in the first place easily increases its size by a couple of orders of magnitude.
Also bonding small rigid things to flexible things is never actually the same as a flexible thing, in several different ways.
These are not equivalent even if you can manage to use either one for some use cases by accepting various compromises.
Alternative 1: Assemble about 3 million individual rigid pixels of an iPhone screen on a flexible substrate, keeping the gaps flexible.
Alternative 2: Produce a single flexible screen piece, requiring no per-pixel assembly.
Which alternative, to your opinion, is likely to cost less?
we make microelectronics as complex as we can because 128 bits would be better than 64 bits, and floating point, and parallelism, pipelining, speculative execution, and caches, etc.
we already make microelectronics as small as we know how, because speed of light makes a difference, and power dissipation also.
and our chips, already completely consumed by the tasks we give them, are too big to fit your definition of flexibility not mattering.
So-ooo-o, if our chips were flexible it would solve the problem we are both trying to solve, which will not be solved your way, except in some uncertain future.
Really, the whole process here is fascinating to me. There's been a lot of progress in flex circuits over this recent decade.
None of it is electrically or computationally new. It's 1980s tech from a computation perspective. But mechanically??
Being able to weave circuits seamlessly into clothes, tapestry, and such is pretty cool. If only for the cosplay / costume designers but that's still a pretty / beautifully kind of display (especially with a few fiber optics to move lights around).
One of the interesting electro-mechanical issues is that flex circuits are necessarily thin, making grounding / return currents exceptionally consistent. On the downside however, solid planes / ground fills are bad for flexibility, so you apparently need to make a ground-grid instead of ground-fill.
Very interesting tech overall. Even if it's applications are quite small right now.
> Flexible... isn't that the point of any central processing unit, to be able to handle many differing types of work?
Oh, pliable? that's cool, I wonder how that works?
No word either on how many bending cycles the product supports.
Still, it's early days, and flexibility might have some use.
the suggested price of a dollar is about 10x worse than something like the py32, ch32v003, or pmc150, which are also faster and more power-efficient
that doesn't mean this is bad research! it just means it isn't yet developed to a state where there's likely to be a market for it. it's very helpful to know that serv occupies 12600 gates, for example, and that the flex-rv process provides 720 gates per square millimeter. it's very plausible you could design something useful with it that had 600 gates, was less than a square millimeter, used 300 microwatts at 60 kilohertz, and cost five cents, for example; that's a niche that silicon photolithography is struggling to fill because of high per-chip costs. you could fit a 6502 into twice that
another potentially interesting niche is low power density; for implanting into your body you don't want hot spots that can burn your tissues (though you'd have to encapsulate the igzo behind something biocompatible)
This is pretty bad from a power efficiency perspective. KHz speed silicon microcontrollers are closer to ~dozens of microwatts, about two decades of magnitude less power than this flex-circuit.
Furthermore, small silicon dies can be placed into flexPCBs. I'm sure a flexchip has more flexibility than a solid silicon die on a flex board but there's a question of how much flex is actually needed in products?
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Still, I recognize that a fully functional CPU on this process is a major achievement. I'm just trying to think of a commercial application, that's all.
But yes, the potential applications are quite limited. Flexible electronics just aren't as useful as people think. I guess it just sounds really cool, like transparent LCDs.
Of course: with the caveat that solid planes of copper are not flexible and will crack. So ground-grid are the best you can do. But physically closer / physically thinner circuits have niche advantages.
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But I'm talking about traditional silicon dies on a flexpcb.
This article is about printing some kind of flexible chip to begin with. It's cool and relatively new, but silicon + flexpcb will be the main technique for e-textiles (and other flex applications) for the near future.
Still, one more tool in the toolbox for electrical engineers. Niche as it is, it's still a tool with likely some good application somewhere.
That’s not correct. It really depends what application, industry and type of testing.
I would say generally it’s the opposite due to worse shielding properties (and worse pi), but it’s a huge oversimplification that’s extremely dependent on application and testing type
It's been an intriguing notion since the time of the dinosaurs, but what is an actual problem that it solves? I've never seen any textile electronics that delivered more than a novelty.
Recreating video game characters in real life is a niche. Cosplay. And there's also e-Fashion that is beyond just copying costumes from video games.
You'll still need to hide the battery box somewhere, and likely also the LEDs are inflexible, but by making more of the circuit etextile / flexible, it allows you to hide the electronics in the clothing itself, woven into the clothes and properly integrated.
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An almost fully rigid design with a few flexible parts (ex: the hinge of the Motorola Fold) is also hot and fashionable right now.
Motorola RAZR (the new foldable screen one) needs a hinge, and the electronics that are integrated into the hinge need to be as flexible as the hinge.
Adding little bits of flexibility, especially to space constrained applications like Phones, does add new useful design features above and beyond "novelty" status, IMO anyway.
I have practically zero knowledge on the physics behind semiconductors to try to think why this could occur but I find it fascinating nonetheless.
+/-5% is a region where everything in the digital domain probably still works. Your rise/fall time and dead-time / other critical timings need to be robust against some degree of variability. Transistors can have rather wide manufacturing variability after all (certainly wider than 5%).
So everything still works but the core clock is changing. Which btw, happens in traditional silicon circuits as they heat up or cool down.
A low precision RC oscillator changing by 5% or so between 20C and 100C is within expectations. I'm fact, a -50%/+100% change wouldn't surprise me.
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Old var-caps (variable capacitors) by twisting them tighter or looser. No joke. So that's where my expectation that they've changed the capacitance of some core element that controls an important clock.
This so-called piezoresistive effect is frequently used for measuring the deformations of various objects, by attaching piezoresistive wires to them, which can measure for instance the amount of bending of the object.
Such a flexible integrated circuit might also have changes in the resistance of the transistor channels or of the interconnection traces, which will change the maximum permissible clock frequency. If an RC oscillator is used to generate a clock signal, its frequency will change with the bending of the circuit, more likely due to variations of the resistance than of the capacitance, because it is not likely for the bending to cause large variations in the thickness of the dielectric of the capacitors or in the area of the electrodes, even if that is also possible.
The variable capacitors whose capacitance is changed by twisting have this behavior because their electrodes overlap only partially and the twisting changes the area of the overlapping region. No such thing happens when twisting or bending a normal capacitor.
Emphasis on _permissible_ clock frequency. Because how is the core logic supposed to figure out how much the clock frequency changed or how much the resistance of the wires have changed?
> because it is not likely for the bending to cause large variations in the thickness of the dielectric of the capacitors or in the area of the electrodes, even if that is also possible.
Yes but no. Everything you said is correct, but you're looking at the wrong dielectric. The plastic PCB is obviously unchanging, even as it gets balled up.
However, there's another dielectric here that's normally ignored that suddenly becomes relevant. The _relevant_ dielectric (to this discussion) is the air. As the capacitor rolls up into a cylinder shape, the copper-air-copper capacitor has the dielectric (air) get thinner-and-thinner.
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However, to your point that this is "resistance"... the fact that "rolling one way" leads to -speed and "rolling the other way" leads to +speed suggests that its a resistance issue. Because the spring/resistance relationship is known. So stress/tension causes resistance of copper to grow, while pressure causes resistance of copper to drop.
If the oscillator is an RC-type oscillator (ex: a 555-timer like oscillator), then yes, I can see the resistance theory playing out. And 60kHz is slow enough that RC-type oscillators are possible.
It is frequent for such logic circuits to use clock generators made with a so-called ring oscillator, i.e. with a chain of inverters containing an odd number of them, which is connected in a loop. The clock period will be a multiple of the delay through a logic inverter.
In this case the actual clock frequency tracks exactly all changes in the permissible clock frequency, regardless of their causes, including temperature and mechanical deformation.
> As the capacitor rolls up into a cylinder shape, the copper-air-copper capacitor has the dielectric (air) get thinner-and-thinner.
I am not sure which is the copper-air-copper capacitor to which you refer. On a PCB, there are parasitic copper-air-copper capacitors between traces, but they have very little influence on clock frequencies. On a normal integrated circuit, there is no air. The metal layers are separated by insulator layers and the top metal is covered by a passivation layer. This flexible circuit should also be covered by some passivation layer.
Replacing in your argument the copper-air-copper capacitor with a copper-insulator-copper capacitor, any circuit has two kinds of capacitors, those that are made intentionally, with two overlapped metal electrodes and a very thin insulator layer between them, and the parasitic capacitors that exist between any metal traces.
Your argument is valid for the parasitic capacitors, because the distance between traces will vary with bending and some parasitic capacitors will become larger, while others will become smaller. The effect of each of the parasitic capacitors on the permissible clock frequency is small and the global effect of all parasitic capacitors is unpredictable without a concrete circuit layout, because their changes with the bending may compensate each other.
For an intentional capacitor, the effect mentioned by you also exists, but in most technologies for integrated circuits the thickness of the insulator of the capacitors is very small in comparison with the lengths and widths of the electrodes. In this case only a very small part of the electromagnetic field is outside the internal space of the capacitor and its influence on the value of the capacitance is negligible. Perhaps the capacitors made with this flexible technology are not as thin in comparison with their area as in other technologies, in which case the effect mentioned by you could be measurable, but I doubt it.
[1] https://www.pragmaticsemi.com/app/uploads/2023/07/Pragmatic-...
In most semiconductor materials it is possible to make good transistors only with a single polarity, either N or P, depending on the material.
So CMOS logic cannot be implemented in most semiconductor materials. This is the main reason why silicon has remained the principal material for complex logic circuits, even if there are a lot of materials with much better properties, except for allowing both polarities for transistors.
In the first decades of the semiconductor industry, the main advantage of silicon had been that it was possible to create a high-quality insulator layer on its surface by oxidation. However there are many years since this advantage is no longer relevant for high-density logic circuits, because all their MOS transistors use now insulators with high dielectric constant, e.g. based on hafnia, which are deposited on the surface of silicon in the same way they would be deposited on any other semiconductor.
NMOS was common in the 1970s before CMOS on silicon was figured out. I'm surprised to hear that this circuit is old-school NMOS, but I probably shouldn't be, as the CMOS step took a lot of research and effort back then....
If we're still at NMOS stage of production on this process, then its probably more relevant to think of analog-based designs. CMOS seems necessary if anyone is to achieve low-power modern-like designs.
NMOS was still core to a lot of older chips though, so digital logic still can work on that. But the power consumption will be necessarily huge in comparison to CMOS.
The 1401 takes 13 kilowatts of juice. So not even in the same universe with respect to power consumed per computation.
They don’t give all details, but I think it’s safe to say there’s work to do w.r.t. performance/Watt, probably more so given that the CPU seems to be bit serial (https://github.com/olofk/serv), which I think means an addition takes 32 cycles.
> The research team found Flex-RV could run as fast as 60 kilohertz while consuming less than 6 milliwatts of power.
Those are TERRIBLE specs compared to silicon. Similar microcontroller specs are 1,000x faster at similar power consumption.
As Moore's Law runs out of steam it is time for the low end applications of computers to shine.
Lots of comments here saying how [relatively] inefficient this is, that utterly miss the point.
Putting cheap, good enough, CPUs into all sorts of places the "efficient " processors cannot go is going to revolutionise all sorts of applications
This is not unique, but representative of its class
Why am I having headaches?