[HN Gopher] A Bendy RISC-V Processor
___________________________________________________________________
A Bendy RISC-V Processor
Author : rbanffy
Score : 175 points
Date : 2024-09-29 14:42 UTC (8 hours ago)
(HTM) web link (spectrum.ieee.org)
(TXT) w3m dump (spectrum.ieee.org)
| eric__cartman wrote:
| > Performance varied between a 4.3 percent slowdown to a 2.3
| percent speedup depending on the way it was bent.
|
| I have practically zero knowledge on the physics behind
| semiconductors to try to think why this could occur but I find it
| fascinating nonetheless.
| dragontamer wrote:
| My expectation is that the core clock circuit has its
| capacitance and/or inductance change, this changing the timing
| of the clock.
|
| +/-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.
|
| --------------
|
| 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.
| adrian_b wrote:
| Many resistive materials, especially those that are
| semiconductors, have changes of resistivity caused by
| mechanical strain.
|
| 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.
| dragontamer wrote:
| > which will change the maximum permissible clock
| frequency.
|
| 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.
|
| -------------------
|
| 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.
| adrian_b wrote:
| > Because how is the core logic supposed to figure out
| how much the clock frequency changed
|
| 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.
| crest wrote:
| Neither do I, but I can tell you if you manage to bend a normal
| CPU die the performance loss is 100% (because you broke it).
| EligibleDecoy wrote:
| What's interesting to me is that it loses 4% efficiency when
| bent. Like, I get why there's some loss because of parasitic
| capacitance/inductance etc but 4% seems like... not very much?
| Someone wrote:
| I guess it helps a lot that it's running at 60kHz.
| https://en.wikipedia.org/wiki/Parasitic_capacitance#Effects:
| _"At low frequencies parasitic capacitance can usually be
| ignored, but in high frequency circuits it can be a major
| problem."_
| Someone wrote:
| > The research team found Flex-RV could run as fast as 60
| kilohertz while consuming less than 6 milliwatts of power.
|
| 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.
| therealcamino wrote:
| From the linked Nature article: "The 5.8 mW power consumption
| is predominantly static (99%) because of the resistive pull-up
| logic."
| yapyap wrote:
| Can't wait to never hear about this again /s
| joelignaatius wrote:
| What's the smallest commercially available electronic and can
| it be inserted into the brain?
|
| Why am I having headaches?
| londons_explore wrote:
| Nearly any uses for flexible electronics would also be satisfied
| by sufficiently small electronics such that lack of flexibility
| doesn't matter.
|
| 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.
| wslh wrote:
| So, nothing particularly interesting here? When I first saw
| 'flexible' I immediately thought about balancing a chip's
| specifications, not its material flexibility!
| dragontamer wrote:
| Flexible circuits are interesting and worthy of discussion.
|
| 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.
| grayhatter wrote:
| It's funny, I thought the exact opposite.
|
| > 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?
| kibwen wrote:
| At a certain threshold, miniaturization of electronics can
| become counterproductive for space applications. The amount of
| radiation received per unit of area remains constant but our
| transistor density keeps increasing, which means that every
| individual event threatens to wreak an increasing amount of
| havoc (e.g. more bits flipped in RAM per cosmic ray).
| Considering the increasing amount of error correction and
| redundancy needed to counter this, we may reach a practical
| floor on transistor density for such domains.
| spwa4 wrote:
| ... which is a huge problem for solar panels ... but why
| would it matter for microprocessors?
| undersuit wrote:
| You don't want transistors operating under the influence of
| outside forces. More than just having a bit flip in your
| data, what if one of the control lines in the CPU flips and
| the entire instruction stream gets corrupted... while
| you're trying to perform orbital maneuvers.
| vmladenov wrote:
| You use multiple processors and a consensus algorithm.
| undersuit wrote:
| You can do that.
| synthos wrote:
| It's also, if not more so, a factor of transistor voltage.
| 1.1V transistors are less prone to upset events than 0.7V.
| It's possible (assumption, here) that some 3+ volt circuits
| are still used for critical components of the system
| adrian_b wrote:
| It would be possible to use much higher supply voltages if
| silicon were replaced with a semiconductor material having
| a higher band gap.
|
| 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.
| mlyle wrote:
| You would need to connect wires to that little 40 um^2 mote to
| do anything, though, which in practice makes the rigid places
| needing strain relief a lot larger.
| marshray wrote:
| It also makes the amount of strain proportionately smaller.
|
| We're talking about a 3mm bend radius here, so there's a few
| orders of magnitude to work with.
| mlyle wrote:
| Not as many as you think, because you need to have targets
| bigger than the ~20um wirebond wire to solder to... and the
| little wire and bond pad are not very tolerant of strain at
| all.
| zozbot234 wrote:
| Leading-edge fab nodes are _way_ too costly for this kind of
| use. Specialty, low-volume chips are the domain of trailing-
| edge tech nodes, sometimes even at the mm level. Besides as
| some sibling comments mentioned, contact pads for off-chip
| wires would get so big as to ultimately take up most of the
| area, so there would be no real advantage to using the finer
| nodes.
| pclmulqdq wrote:
| Most microcontrollers today are using 40-90 nm processes.
| That's not the micron level at all. Chips that need current-
| handling capabilities or have weird needs will use bigger
| process nodes. This is a big part of why automotive
| electronics use old nodes.
| addaon wrote:
| 40 um^2 might cover the logic (although I think your logic
| transistor count is a factor of three low; and something like
| this is most likely to be made on a 45 nm or bigger process),
| but doesn't cover IO pads. If you're willing to wire bond
| directly to a flex circuit you may be able to use pads on to
| order of 50 um x 50 um (each! Likely need 6 or 8 pads to be
| useful), but that's a hell of a process, and you'd have to
| encapsulate afterwards, adding bulk. If you want to flip-chip
| mount it's pretty hard to go under 1 mm x 1 mm for a useful
| microcontroller, although there's some stuff out there at 600
| um x 600 um or so from memory -- but pad sizes under 300 um
| then bump up your resolution requirements for the flex circuit
| you're bonding to.
| Brian_K_White wrote:
| What are the fab requirements of the two techs? If the ffc
| version can be manufactured with as basic tech as ffc, then
| that is huge.
|
| 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.
| alted wrote:
| Ignoring flexibility and cost/performance, this may be a sign
| that rapid chip fab turnaround times are possible. These were
| made by Pragmatic Semiconductor [1], who claim they can make
| chips within 48 hours and deliver within 4 weeks (likely due to
| their use of unconventional materials). Traditional silicon
| fabs, including trailing-edge foundries and TSMC, take 2-9
| months. I do wish they'd emphasized this instead of
| flexibility.
|
| [1] https://www.pragmaticsemi.com/
| IshKebab wrote:
| Yeah but traditional silicon fabs aren't making 12k gate
| chips.
| Teever wrote:
| What's the turn around time on 12k gate chips from a
| traditional fab?
| dragontamer wrote:
| Just googling really quick: the Lattice Semiconductor
| LFE5U-12 is a 12k-LUT FPGA (and a LUT is way more
| flexible than a gate).
|
| 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.
|
| -------------
|
| 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.
| rkangel wrote:
| The power profile of an FPGA is very different (worse)
| than dedicated silicon. Both the background current and
| cost of a gate switch. There are a lot of situations
| where that isn't acceptable.
| londons_explore wrote:
| I suspect the power profile of an FPGA is better than
| this flex-silicon...
| rkangel wrote:
| True, that's definitely possible. I was giving the
| habitual answer (that I occasionally need to explain to a
| client at work) why you need to spend $2m having an ASIC
| made when "it's just digital logic and we got the
| prototype going in a month"
|
| They usually care about at least one of - size, power,
| cost.
| ChuckMcM wrote:
| Some questions you might consider which would help you to think
| of some use cases;
|
| 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.
| saulrh wrote:
| > 1) How would wiring to you processor work?
|
| 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.)
| marshray wrote:
| > or you spend twenty hours soldering nearly microscopic
| bits of magnet wire to it.
|
| 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.
| ChuckMcM wrote:
| You can look at die attach[1] which basically solders to
| pads on the circuit board (no magnet wires required :-)).
|
| [1] "Die Attach Comes to PCBs" ---
| https://www.eeweb.com/die-attach-comes-to-pcbs/
| marshray wrote:
| > 1) How would wiring to you processor work?
|
| 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.
| ChuckMcM wrote:
| Yes, the entire chip (wiring and transistors) is flexible.
| Which is something I find kind of amazing. Back in 2008
| there was a company in the UK called 'Plastic Logic'[1]
| that was going to make an e-reader that could be rolled up.
| Back when organic LEDs were just starting to be possible
| and this stuff was living on a glass substrate, doing "all"
| of the circuits in long change hydrocarbons was a pretty
| revolutionary idea.
|
| 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/
| nine_k wrote:
| > _you make each pixel rigid and have the joints between pixels
| flexible_
|
| 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?
| leptons wrote:
| The article is about a CPU, not a display technology - there's
| a big difference in functionality and fabrication between those
| two things, so your iPhone screen pixel example doesn't really
| fit this use case.
|
| 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.
| wyldfire wrote:
| Don't you have to put those BGAs on some kind of pad?
| dragontamer wrote:
| > Each Flex-RV microprocessor has a 17.5 square millimeter core
| and roughly 12,600 logic gates. The research team found Flex-RV
| could run as fast as 60 kilohertz while consuming less than 6
| milliwatts of power.
|
| 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?
|
| ---------
|
| 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.
| mystified5016 wrote:
| E-textiles, probably. There's a small, but real, niche trying
| to put circuitry onto/into fabrics. Traditional flex PCBs get
| you pretty close, but any large IC creates a limited bend
| radius and a stress point that will fail very quickly. Using
| lots and lots of tiny dice for this would _technically_ work,
| but it 's extremely impractical unless you're building your
| widget by the millions.
|
| 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.
| dragontamer wrote:
| The thin nature of flex circuits have interesting
| implications for capacitance / parasitic inductance. I've
| been told that flex circuits are far easier to pass EMC
| testing due to the physically closer ground/reference return
| path.
|
| 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.
|
| -------
|
| 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.
| shadowpho wrote:
| >I've been told that flex circuits are far easier to pass
| EMC testing
|
| 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
| vpribish wrote:
| "a small, but real, niche" - is it though?
|
| 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.
| dragontamer wrote:
| A lot of video game characters, especially SciFi ones, have
| glowing clothes of some kind with mesmerizing patterns. The
| easiest way to create this effect is a combination of
| etextiles, LEDs and maybe some fiberoptics (which are also
| flexible enough to be woven into clothing).
|
| 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.
|
| ------------
|
| 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.
| 6SixTy wrote:
| This is mostly for medical applications. Wearable, maybe
| implantable, electronics for monitoring vital signs are a real
| thing that could completely change form with flexible
| processors.
| kragen wrote:
| 60 kilohertz on 6 milliwatts sounds pretty bad (that's 100
| milliwatts per megahertz and so 20 milliamps per megahertz if we
| assume 5 volts, while 0.06 milliamps per megahertz is common for
| low-power processors) but it's actually far, far worse than it
| sounds because serv is bit-serial, requiring, i think, 32 cycles
| per instruction. so you're looking at something like 5000 times
| the energy consumption of existing off-the-shelf microcontrollers
|
| 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)
| ForestCritter wrote:
| Because wrapping it around a pencil is clearly a benefit(:
| Conscat wrote:
| Flexible PCBs are convenient to embed in fabric.
| vitiral wrote:
| This is super exciting, I love to see advances in low temperature
| semiconductor manufacturing. HOWEVER
|
| > 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.
| gradschool wrote:
| Any ideas on why they'd use NMOS [1] instead of CMOS if they're
| aiming for low power? Too many layers? My (amateur, outdated, and
| probably wrong) recollection is that CMOS dissipates very little
| power except when switching, but not so for NMOS.
|
| [1]
| https://www.pragmaticsemi.com/app/uploads/2023/07/Pragmatic-...
| dragontamer wrote:
| CMOS requires very tight tolerances for the PMOS + NMOS
| transistors to cancel each other out exactly. Otherwise it
| doesn't work at all. In particular, you need to ensure that the
| PMOS and NMOS turn on at the same voltage, otherwise you risk
| just shorting Vcc to Vss (aka: Power to Ground).
|
| 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.
| adrian_b wrote:
| Only in few semiconductor materials it is possible to make good
| transistors with both polarities, silicon, germanium and the
| silicon-germanium alloy being the main examples.
|
| 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.
| ddtaylor wrote:
| The positioning of this product is strange to me. The features
| and specs of the product don't seem very impressive, as others
| have pointed out, and the overall tone of the writing suggests
| someone who found something and is looking for what drawer it
| goes in.
| worik wrote:
| Very cool.
|
| 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
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