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'Reversible' Computers More Energy Efficient

Hemos posted more than 10 years ago | from the faster-but-does-it-work dept.

Technology 330

James Clark writes "As Congress continues work on a federal energy bill, a group of University of Florida researchers is working to implement a radical idea for making computers more energy efficient -- as well as smaller and faster." Reversible computing rears its head again.

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FP FP FP (-1)

Anonymous Coward | more than 10 years ago | (#7447427)

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Re:FP FP FP (-1, Offtopic)

Anonymous Coward | more than 10 years ago | (#7447680)

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Vaporware? (4, Interesting)

Carnildo (712617) | more than 10 years ago | (#7447443)

Has anyone ever built even a very simple reversible computer? Or is this like quantum computers: all theory, no practice?

Re:Vaporware? (4, Informative)

nestler (201193) | more than 10 years ago | (#7447517)

This is more practical than quantum computers because it is much easier to build and can be used for general purpose things other than search and factoring.

The idea is to (down at the gate level) keep everything reversible. For example, current OR gates are not reversible (given a true output you can't definitively tell what either input was individually). If you have two outputs on the gate instead of one, you make the gate reversible. However, since you are just using it for OR, you are free to ignore the second bit you added on to make it reversible.

The bit doesn't help your computation in the sense of the answer you are looking for, but it can make things more energy efficient at the gate level.

HOW does it make it more efficent? (3, Interesting)

autopr0n (534291) | more than 10 years ago | (#7447679)

I mean, say you have a CMOS OR gate. If both of the inputs are high, then the NMOS transistors will close and the PMOS transistors will open. Energy is lost only when electrons 'leak through' when the gate changes (and of course, electrons that leak through but don't affect the computation, which I guess happens all the time). How would reversing the computation affect this? Maybe if you were using plain PMOS or something...

Re:HOW does it make it more efficent? (2, Informative)

mikeee (137160) | more than 10 years ago | (#7447744)

Well, there isn't exactly a how. Thermodynamics guarentees us that non-reversable gates will use energy. It doesn't guarentee that it's possible to build a reversable one that doesn't; it does guarentee that any gate which doesn't lose energy is reversable.

Re:HOW does it make it more efficent? (5, Informative)

randyest (589159) | more than 10 years ago | (#7447757)

Enegy is lost always (leakage current) because the gate is not a perfect insulator. The smaller the gates, the more ther leakage. This is called static power.

Energy is also lost during switching, as the charge needed to switch is moved around. This is called dynamic power.

Reversible computing endeavors to reduce/eliminate dynamic power. It does nothing for static power. A long time ago, dynamic power was dominant and static power was negligble. Now, gates are so small, static power is approaching the same order of magnitude as dynamic.

So, even though they're only addressing about 1/2 of the problem, it would be great to have the magnitude of that big problem halved.

Re:Vaporware? (5, Informative)

randyest (589159) | more than 10 years ago | (#7447722)

I think you completely misunderstood the article, though in your defense it didn't do a very good job of explaining. The idea is not to be able to reverse logical operations -- that is of little value to anyone. Rather, they're trying to make the electrical changes (the energy transfer) reversible. That's a fundamentally differeent thing. A decent analogy, mentioned in the article is:

The concept is somewhat analogous to hybrid cars now on the market that take the energy generated during braking and recycle it into electricity used to power the car.

So, the logical realm is no different here. Physically, and electrically, there is a big difference from existing computers. Now, when a bit changes from 1->0, the voltage (accumulated charge) is simply shorted to ground (via resistive path that dissipates heat). That energy is lost. In a reversible computer, that charge would be stored, in the electrical equivalent of a spring or flywheel in a mechanical system. So, next time it needs to go 0->1, the energy is sitting there, ready to be re-used(stored in the spring's compression or flywheel's rotation).

I assume these electrical "springs or flywheels" need to be phsycally close to the transistors they're storing energy for. If all transistor's storage were common, the heat loss (and time delay) to get the energy back to where it's needed would defeat the entire purpose.

In the article, they mention that current prototypes use oscillators to store the energy (which are more like a flywheel than a spring, to continue the mechanical analogy), but the efficiency is not quite good enough to be called "reversible". Too much energy is lost in storing and un-storing the energy. The current work is focused on improving the efficiency of storing and un-storing energy from state changes.

However, as a chip designer, I know that oscillators are usually (1) much much bigger than simple logic gates and (2) much more difficult to design with (it's analog design stuff, really). So, my concerns are (1) how much bigger will dice need to be to use this system (linear increase in die size equals exponential increase in manufacturing cost) and (2) how much longer is it going to take to close a design with all those little analog cells all over the place.

I don't even want to think about the implications for STA (static timing analysis) or LVS (layout versus schematic verification) -- it makes my head hurt. :)

Re:Vaporware? (2, Informative)

stoolpigeon (454276) | more than 10 years ago | (#7447532)

The answers to your questions are in the article - here:

Frank, who first worked on reversible computing as a doctoral student at the Massachusetts Institute of Technology, heads UF's Reversible & Quantum Computing Research Group. Among other recent publications and presentations, he presented three papers dealing with topics related to reversible computing this summer, including "Reversible Computing: Quantum Computing's Practical Cousin" at a conference in Stony Brook, N.Y.

and here:

Frank currently is trying to persuade major chipmakers to direct more of their research-and-development resources toward reversible technologies.

From the article... (2, Informative)

TamMan2000 (578899) | more than 10 years ago | (#7447543)

While he was at MIT, Frank worked on a team that built several simple prototypes of reversible chips.

It has at least gotten to the chip level so far...

Re:From the article... (0)

Anonymous Coward | more than 10 years ago | (#7447616)

Wtf this is /. -- quit reading the articles.

OK Homer quote (1)

LittleBigScript (618162) | more than 10 years ago | (#7447574)

Homer: I know. And this perpetual-motion machine she made today is a joke! It just keeps going faster and faster. In this house, we obey the laws of thermodynamics!

Re:Vaporware? (0)

Anonymous Coward | more than 10 years ago | (#7447591)

I hate to be the one to break it to you, but quantum computers are not all theory.

Photographs of "a very simple reversible computer" (3, Interesting)

Dlugar (124619) | more than 10 years ago | (#7447747)

Universiteit Gent [rug.ac.be] has some pictures of reversible logic gates, including a four-bit adder composed out of Feynman's "NOT, the CONTROLLED NOT, and the CONTROLLED CONTROLLED NOT" reversible logic gates, and some other circuits they've built.

They also have links to other sites about reversible logic and reversible computing, such as Ralph Merkle's Reversible Computing page [zyvex.com] (from Xerox).

Also note the bottom of the page: there's a vacancy in the research group, [ugent.be] for all those just aching for a chance to work on reversible computing! (Looks like you'll have to speak Dutch, though.) ;-)


Dlugar

Not too bad an idea, BUT... (1)

ghettoboy22 (723339) | more than 10 years ago | (#7447447)

I know of more than one building who relys on the heat produced by the computers as the sole source of heating. But it is good for OC'ing!

pateNTdead eyecon0meter: gravity still exists? (-1, Offtopic)

Anonymous Coward | more than 10 years ago | (#7447448)

appears so. get ready....

Re:pateNTdead eyecon0meter: gravity still exists? (-1, Offtopic)

Anonymous Coward | more than 10 years ago | (#7447455)

where have you been?
I miss your insightful and inspiring words.

mynuts won? creators' newclear power omnipotent? (0)

Anonymous Coward | more than 10 years ago | (#7447642)

you can bet your highly mortgaged .asp it is. the most advanced energy transmission, open/honest communications systems in the universe. this stuff is unbreakable, & wwworks on several (more than 3) dimensions. it would, of course, almost have to be, considering the execrabilities of unprecedented evile et AL.

Due to excessive bad posting from this IP or Subnet, comment posting has temporarily been disabled. If it's you, consider this a chance to sit in the timeout corner. If it's someone else, this is a chance to hunt them down, (& rat them out, for monIE, LIEk with fuddles' softwar gangster bouNTy scam)? If you think this is unfair, we don't care.

mynuts won: get ready to see/hear/feel something?

Reversed! (1)

dolo666 (195584) | more than 10 years ago | (#7447453)

Imagine all the cool things you could do with the heat from your computer, instead of directing back to the system... *gasp-heartfailure*

Hallelujah! (1)

mblase (200735) | more than 10 years ago | (#7447618)

I, for one, am all for this. Providing machines with a way to reclaim their own heat energy for power is the only way to ensure we don't all end up jacked into a computer-generated Matrix so they can suck up ours.

Ya'll got that computer on backwards... (0)

Traicovn (226034) | more than 10 years ago | (#7447454)

I thought the computer I had was reversible, but unfortunately somebody told me that it wasn't. And I thought when I had it off it was on. Shoot.

This job used to be more fun.

Reversing entropy? (2, Interesting)

oGMo (379) | more than 10 years ago | (#7447459)

IANAP, but this sounds like trying to reverse entropy as much as possible to me. Won't it take more energy to do a reverse computation than you'll save? Where does the lost energy from that go?

Re:Reversing entropy? (0)

Anonymous Coward | more than 10 years ago | (#7447511)

Homer: "Lisa, in the house we obey the laws of thermodynamics!"

Re:Reversing entropy? (2, Informative)

Carnildo (712617) | more than 10 years ago | (#7447544)

There are two theories about energy usage during computation. One is that moving and transforming data requires energy. The other is that the only operation that requires energy is destroying data. Reversible computing subscribes to the second theory, so a reversible computer would not actually use energy to do computations (apart from the inevitable inefficiencies). Since there is no net energy usage, the net entropy neither increases nor decreases, and the second law of thermodynamics doesn't apply.

Re:Reversing entropy? (1)

jc42 (318812) | more than 10 years ago | (#7447707)

I've long been curious about this idea of destroying data inside a computer. It seems to me that before and after any opcode, your typical computer contains exactly the same amount of data. A few bits have changed from 0 to 1 or vice-versa. But the number of bits is the same, and each contains only one bit of data, so the amount of data is the same.

So far, when I've questioned people about this, I always get a response that amounts to saying "Boy, you must be a real idiot if you don't understand this." This may be true, but it's not an explanation, it's just a way of refusing to explain anything.

So whatever does it mean to talk about a computer destroying data?

Re:Reversing entropy? (0)

Anonymous Coward | more than 10 years ago | (#7447705)

Take a course in thermo or in stat mech and you will learn that there are reversible and irreversible processes. The point here is not to "reverse entropy" (whatever that may mean) but to try to minimize the increase in entropy for the system.

Now, an irreversible process in general will still increase the total entropy. But the closer it is to being adiabatic, the less the increase in entropy will be. Whereas with an irreversible step, the increase in entropy is totally unavoidable, and all you can do about it is to shrink the system or to do the step less often.

Re:Reversing entropy? (1)

cavemanf16 (303184) | more than 10 years ago | (#7447709)

I imagine this system would simply involve designing less wasteful logic gates than currently exist, in which AND, OR, and XOR gates send excess voltage inputs back through the circuit, allowing the power supply to use the energy again rather than throw it off as heat.

Remember, in the most simple OR gate, if you have two input voltages of +5V each, the output will only be +5V, leaving that additional +5V to be thrown off as heat. Sounds like this story is talking about some kind of logic gate that "recirculates" those 'extra' +5V signals back to the power supply system.

But don't take my word for it... I've only had some of the more basic circuit analysis and design courses to date. ;)

"Reversible" a bad name? (4, Insightful)

cant_get_a_good_nick (172131) | more than 10 years ago | (#7447462)

Wouldn't "regenerative", like regenerative braking on most electrics/hybrids been a better term?

Would not a CPU by anyother name produce as much Q (0)

Anonymous Coward | more than 10 years ago | (#7447556)

No, they should have been called Carnot Cycle Computers. Then we could call them CCCPU's and talk about beowulf clusters in post-Soviet Russia and get modded 'informative'.

Re:"Reversible" a bad name? (2, Insightful)

Anonymous Coward | more than 10 years ago | (#7447682)

This is an area where information theory and physics meet. To minimize heat you must minimize entropy production and that means you must in fact make your computations reversible, as much as possible.

Sounds good, but... (2, Insightful)

Tin Foil Hat (705308) | more than 10 years ago | (#7447470)

I have to admit that I'm no chip designer, but I have to wonder why this hasn't been done before? What are the problems with this technic?

It sounds good, but what's the catch?

Re:Sounds good, but... (4, Informative)

pclminion (145572) | more than 10 years ago | (#7447533)

Because it seemed totally pointless. It was a theoretical curiosity.

People started looking at reversibility in earnest when quantum computing came on the scene. A quantum computer HAS to be reversible in order to function. That made it a very important field of study.

We only recently realized that reversible circuits are also more energy efficient. So basically, we didn't do it before because we didn't know. There is no "catch."

Re:Sounds good, but... (1)

mikeee (137160) | more than 10 years ago | (#7447684)

Although it should have been obvious all along, and probably was if anyone cared. It follows directly from thermodynamics, although the result is a little odd; in essence, there's no theoretical lower bound on how much energy it takes to compute; it's forgetting that takes energy. Ergo, in theory a computer that never loses any data (is reversable) doesn't necessarily use any energy.

re: sounds good, but... (1)

ed.han (444783) | more than 10 years ago | (#7447697)

stupid question perhaps but doesn't this in essence require something like a database in order to store, arrange and recall the desired results? am i missing something here?

b/c if that's true, then does this mean some day in a few decadees, someone's gonna introduce a relational--

[gets killed by angry mob of unemployed DBAs]

ed

How exactly am I supposed to ... (4, Funny)

burgburgburg (574866) | more than 10 years ago | (#7447473)

fry eggs [hex-tech.co.uk] if this sort of thing becomes the norm?

Insensitive clod!

Reversible Computing (1)

JamesD_UK (721413) | more than 10 years ago | (#7447474)

Before I read the article, I saw the title and assumed someone had designed a computer that gave me answers before I'd even decided what program to run. :-) Useful for those moments where I find myself sitting down at the computer, wondering what it was I was meant to be doing. Current solution to my problem: load up slashdot and wait a little while.

sort of like recycling.... (4, Funny)

smd4985 (203677) | more than 10 years ago | (#7447477)

your computer could spit out: "these CPU cycles made of 75% post-CPU-consumed waste" :)

Something to worry about... (4, Funny)

Nom du Keyboard (633989) | more than 10 years ago | (#7447478)

In fact, unless reversible computing is achieved, computer chips are expected to reach their maximum performance capabilities within the next three decades

Boy, that's something to worry about today. I'll just have to find a spot to insert it on my Worry List. Maybe I can drop Global Warming to make space.

Re:Something to worry about... (1)

Carnildo (712617) | more than 10 years ago | (#7447606)

Assuming Moore's law continues to apply until then, that means that those computers will be a million times faster than the ones available now.

So, what do you plan to do with your 3 exahertz Pentium 17?

I have one of those jackets ... (1, Offtopic)

didjit (34494) | more than 10 years ago | (#7447479)

Its cool cause sometimes I feel like wearing blue and sometimes black. They work best on an every other day cycle. People think I can afford two jackets.

Sigh... I knew I shouldn't RTFA (5, Funny)

winkydink (650484) | more than 10 years ago | (#7447482)

Here I thought it was an Intel box that, when turned inside out, became a Mac.

Sigh.

Re:Sigh... I knew I shouldn't RTFA (1)

shish (588640) | more than 10 years ago | (#7447710)

Intels are beautiful on the inside? Macs aren't?

Cool (1, Interesting)

pclminion (145572) | more than 10 years ago | (#7447489)

Yet more evidence that information is in fact a quantifiable property. We're starting to see hints that information and energy are flip sides of the same coin.

I'm not just spewing. There are serious theoretical problems associated with how information "disappears" when it falls into a black hole. Fortunately, you get the information back again from Hawking radiation, as the hole converts mass into energy. From a theoretical standpoint it's really starting to look like "information == energy," or to put it more precisely, there is a specific equivalence between information and energy like the equivalence between matter and energy.

We've already got space == time, matter == energy, why not also information == energy? There are starting parallels between Shannon's information theory, and the theory of thermodynamics. There is some mysterious shit going on here.

Another boost to my pet theory of the universe: everything is equal to everything else, and we delude ourselves into perceiving imaginary distinctions between things.

Re:Cool (1)

gowen (141411) | more than 10 years ago | (#7447550)

We've already got space == time, matter == energy, why not also information == energy? There are starting parallels between Shannon's information theory, and the theory of thermodynamics. There is some mysterious shit going on here.
I'm not a theoretical physicist, but I thought the equivalence was more along the lines of

Information = order = !entropy

and it was entropy constraints that gave rise to Hawking Radiation.

Re:Cool (1)

gordyf (23004) | more than 10 years ago | (#7447588)

everything is equal to everything else, and we delude ourselves into perceiving imaginary distinctions between things.

Sounds like a really good hit of acid, to me...

S is for the work I'm not allowed to do... (0)

Anonymous Coward | more than 10 years ago | (#7447664)

I find your pseudo-religious philosophical babbeling intriguing. I was wondering where I might go to obtain a pamphlet with dire predictions for the comming appocolypse.

PS - Would it be alright if I wore Nike's to the winter solstice tinfoil hat mixer? Or is it semi-formal? I, of course, trust there will be kool-aid.

Re:Cool (2, Informative)

Have Blue (616) | more than 10 years ago | (#7447673)

Energy is equivalent to WORK. Information is a static property of a configuration of elements.

What's going on here is a circuit implementation detail. In a normal chip, when you have a bit set to 1 and a bit set to 0 and you flip them both, the bit set to 0 is charged with fresh energy from the power supply and the energy in the bit set to 1 is converted to heat. In this proposed system, the charges would be moved from the 1 to the 0 with no loss and no additional draw on the power supply. Less work, same informational content.

Re:Cool (2, Insightful)

hchaos (683337) | more than 10 years ago | (#7447748)


Yet more evidence that information is in fact a quantifiable property. We're starting to see hints that information and energy are flip sides of the same coin.

I'm not just spewing. There are serious theoretical problems associated with how information "disappears" when it falls into a black hole. Fortunately, you get the information back again from Hawking radiation, as the hole converts mass into energy. From a theoretical standpoint it's really starting to look like "information == energy," or to put it more precisely, there is a specific equivalence between information and energy like the equivalence between matter and energy.


Actually, you are just spewing, at least kind of. As long as the Second Law of Thermodynamics holds true, there is no "conservation of information" law in this universe.

What's really happening here is a lot more simple. In a digital computer, information is stored as a series of energy states. A bit is either 1 or 0, with a 1 meaning that a circuit is energized, while a 0 means that the circuit is not energized. The important thing is that both energized and non-energized circuits hold exactly the same amount of information.

The only thing that this article is talking about is storing the energy from the energized bits in an "energy cache" once the 1 has been switched back to 0, so it can then be used to power other bits. It's really not a very radical idea at all. The only semi-radical thought here is that it would be worthwhile to recover this energy, and that chip manufacturers would benefit from investing in this research.

Patent office would love this (1, Funny)

bugnuts (94678) | more than 10 years ago | (#7447490)

A Perpetual Computing Machine!

Turn it on and it generates cycles from microscopic springs and pulleys, we call "Springons" that can recover the computing power expended, sending the cpu "Wheel" into another revolution.

--

funny how all these machines require a battery or plug.... :-)

WTF is reversable computing? (1)

EvilTwinSkippy (112490) | more than 10 years ago | (#7447501)

Energy efficient, got you. But as an Electrical Engineer, and a seasoned network engineer, I've never heard the term before. And I'm pretty damn well read.

Re:WTF is reversable computing? (1, Informative)

pclminion (145572) | more than 10 years ago | (#7447568)

It means you can take the outputs and recover the inputs.

If I tell you that (x && y) == 0, can you tell me what x and y are? No: it could be (0, 0) or (0, 1) or (1, 0). Therefore, the operation AND is not reversible.

A reversible computer always performs operations that can be uncomputed. Given the outputs, you can reconstruct the inputs. This means, for one thing, that a reversible computer has no concept of boolean AND. Or OR, for that matter. NOT is reversible, though.

Re:WTF is reversable computing? (1)

Sebastopol (189276) | more than 10 years ago | (#7447599)

Unfortunately, only NOT is reversible. (Name one other gate that is? ... buffers don't count ;-)

So that gets us nowhere.

I believe the article is hinting at reusing the charge required to change state. Although I have no idea how it is stored, or how it is re-routed.

This article is entirely fluff.

Re:WTF is reversable computing? (1)

pclminion (145572) | more than 10 years ago | (#7447646)

Well, AND and OR aren't reversible, but that doesn't mean there are no binary operations that aren't. It just means that a reversible computer is going to work a lot differently than you are used to.

In particular, most reversible logical operations have more than one output. The example of NOT is one of the few than has only a single output.

So if they are "reversable", (0)

Anonymous Coward | more than 10 years ago | (#7447509)

does that mean a Beowulf cluster of them would actually run slower? ;)

Wrong tagline... (2, Funny)

Anonymous Coward | more than 10 years ago | (#7447513)

Should be "Reversible computing rears its butt again"

This is perfect for Microsoft... (1, Funny)

ConceptJunkie (24823) | more than 10 years ago | (#7447515)

You can start with the Blue Screen of Death and acheive any functionality.

Re:This is perfect for Microsoft... (1)

nmg (614483) | more than 10 years ago | (#7447577)

least funny comment on slashdot ever

Re:This is perfect for Microsoft... (0)

Anonymous Coward | more than 10 years ago | (#7447640)

...and quite possibly the funniest flame ever. Simple and direct.

Re:This is perfect for Microsoft... (1)

Artifakt (700173) | more than 10 years ago | (#7447674)

But only if the OS version counts down - 94 - 93 - 92... each time you turn it on.

Re:This is perfect for Microsoft... (1)

DarkSarin (651985) | more than 10 years ago | (#7447734)

interesting sig, but generally see the orginal quote attributed to Isaac Asimov, not Arthur C. Clarke.

Can you provide a source? I can--look up the book "Magic" by Asimov on amazon, and read that. Also the Foundation books that have been written in his honor by (I think) Greg Bear and others also reference this quote.

Re:This is perfect for Microsoft... (0)

Anonymous Coward | more than 10 years ago | (#7447714)

It'd be sweet for linux too. You'd be able to start at kernal panic and acheive the functionality of MS-DOS 3.2!

Heated my first apartment (1)

BWJones (18351) | more than 10 years ago | (#7447519)

.....it also could boost their speed, because these chips are becoming so fast that the heat they generate limits the speed at which they can operate without overheating and malfunctioning.

Bah, this idea is nothing new. From the two SGI's with two 20in displays, two macs and five displays attached to them, my tiny little first apartment had more than enough heat production to warm things up. :-)

What about cars? (0, Offtopic)

xanderwilson (662093) | more than 10 years ago | (#7447521)

Don't cars still use less than 50% of the energy they consume and the rest is released as heat? If we haven't figured that out yet on a longer timeline, then how long do they expect this to take? And if it is realistic, then how much more powerful are oil companies politically than electric power companies that the latter are going to just stand by and let this happen?

Alex.

Re:What about cars? (1, Informative)

Anonymous Coward | more than 10 years ago | (#7447675)

Internal combustion engines used in mass market automobiles have an efficiency of closer to 18%. Pretty horrible, really.

The energy lost is through exhaust heat, water heating, and friction.

Re:What about cars? (4, Informative)

Jerf (17166) | more than 10 years ago | (#7447694)

And if it is realistic, then how much more powerful are oil companies politically than electric power companies that the latter are going to just stand by and let this happen?

You mean, the power companies are going to force Intel to make their chips more wasteful, causing progress to halt and people to buy fewer Intel chips? Yeah, sure.

I mean, there's paranoia, and there's paranoia.

Come on, wake up. I won't claim that kind of thing never happens but by and large capatalism is too powerful; Intel isn't going to act against its own best interests for any mere money the power companies can throw at it, because it won't be worth it. Growth is worth more then mere money to Intel. (If you don't understand why, go learn about business; the explanation is too complicated for a Slashdot posting.)

The power company is made of people like you and me; far too busy to hover over various scientific journals and swoop around like super-villians repressing "dangerous" information.

Re:What about cars? (2, Informative)

Carnildo (712617) | more than 10 years ago | (#7447717)

Even a perfect internal combustion engine can't be more than about 25% efficient, because of the nature of heat engines. Cars are already getting pretty close to this limit, so any improvements to fuel efficiency will come from techniques like lighter-weight vehicles, better aerodynamics, and techniques like hybrid engines that let the engine run at top efficiency all the time.

Horrible article (0)

Logger (9214) | more than 10 years ago | (#7447525)

What a horribly written article, it says precisely NOTHING. Anyone have a link to something with more detail than, "rather than building up and tossing away unwanted information, the chips "uncompute" it fluidly?"

Uncompute? This does NOT compute!

How about something that describes information like:

1) Is this a transistor based circuit? If so, it's a far cry from todays traditional CMOS structures.
2) How do they plan to charge and discharge the transistor/capacitors/whatever in a way that conserves energy?

Read the Feynman book (3, Informative)

rarose (36450) | more than 10 years ago | (#7447612)

http://www.amazon.com/exec/obidos/tg/detail/-/0738 202967/103-2222180-5559862?v=glance

He has a great deal of info about how reversable computers work and why they save energy.

Re:Read the Feynman book (0)

Anonymous Coward | more than 10 years ago | (#7447670)

And $4.35 cheaper than B&N.com!

Re:Horrible article (1)

Crimson Midget (41436) | more than 10 years ago | (#7447653)

I refer you to a decent article on Kuroshin:
http://www.kuro5hin.org/story/2003/9/8/ 14125/70302

I also suggest MIT's reversible computing page:
http://www.ai.mit.edu/~cvieri/reversible.ht ml

and there's:
http://www.supercomputingonline.com/arti cle.php?si d=4894
http://www.spie.org/conferences/calls/01/a m/confs/ AM429.html

This seems really confusing! (1)

MooseGuy529 (578473) | more than 10 years ago | (#7447528)

Correct me if I'm wrong, but does this just take the energy from the ground of a component and pull it back into a power source? Couldn't you just do this by putting a capacitor on the ground and switching to it occasionally instead of... (train of thought derailed) So it basically takes electricity and pushes it between a capacitor and a circuit? That's clever, but I thought the heat just came from all the electricity "moving around" so much--won't this just make it move back in the same direction instead of to ground? And, if done right, couldn't this make really energy-efficient processors? And if you made a multi-processor system where one processor runs off positive voltage and the other runs of negative voltage, could you wire this up to be *really* efficient?

Just some ideas, flame/reply away...

Theory (1)

cristofer8 (550610) | more than 10 years ago | (#7447536)

The idea here is that when you use any 2->1 gate, such as an and gate, you lose one bit of information. Since information is actually just energy, you have to dissapate that energy somewhere, usually as heat. If instead of a 2->1 gate you used 2->2 gates, where one bit is the and product and the other is enough information to reverse the operation, you aren't discarding any information and thus, aren't dissapating any heat.

No more breakfast (1)

AtariAmarok (451306) | more than 10 years ago | (#7447538)

I was so used to cooking breakfast on the top surface of my Apple Cube [wired.com] . I'll miss this if the energy gets recylcled elsewhere, and I'll likely have to go buy a Foreman grill to make up for the loss of this nifty cooking appliance.

At long last! Reversable computing! (1)

bugnuts (94678) | more than 10 years ago | (#7447559)

Finally a hardware device that can decrypt backwards writing.

Now if only they'll invent Transposed Computing that can hardware decrypt Rot13.

3 decades? (0)

Anonymous Coward | more than 10 years ago | (#7447563)

Glad the author didn't step out on a limb or anything with the prediction that current microprocessors will hit a ceiling in 3 decades...

Shit, I thought my computer could run backwards (1)

Saint Stephen (19450) | more than 10 years ago | (#7447569)

I wish my computer was reversible in the sense that I could press the rewind button and everything I did would happen in reverse.

I'm telling at as a joke, but I've always wondered why no chip designer ever wrote this. It should be possible to log every instruction that passes through the CPU and play them in reverse order. Imagine how cool that would be!

How much is that? (-1, Troll)

RevMike (632002) | more than 10 years ago | (#7447571)

According to the article, current CPUs put out about 100 Watts as heat. How much is that? Can anyone give me a decent comparison to an ordinary houshold object that would allow me to fathom how much power that is?

Re:How much is that? (1)

z4ce (67861) | more than 10 years ago | (#7447636)

I would imagine about as much as a 100watt light bulb... All of the 100 watts has to end up as heat in your room some how.. :)

Ian

Re:How much is that? (1)

Theaetetus (590071) | more than 10 years ago | (#7447650)

According to the article, current CPUs put out about 100 Watts as heat. How much is that? Can anyone give me a decent comparison to an ordinary houshold object that would allow me to fathom how much power that is?

Sure! A 100 watt lightbulb. Glad I could help. ;)

-T

Re:How much is that? (0)

Anonymous Coward | more than 10 years ago | (#7447708)

It's about about as much power as a 100 Watt light bulb.

Reversable memory? (1)

autopr0n (534291) | more than 10 years ago | (#7447573)

It seems to me that what they are saying is that most of the heat comes from memory elements being discharged. What about energy spent by fliping a CMOS gate? Isn't that where most of the power is lost? I mean, even CPUs that only have very small on-die caches still generate a lot of heat.

Thermodynamics 101 (5, Informative)

majid (306017) | more than 10 years ago | (#7447595)

You get the most energy efficiency from a machine when it works in a thermodynamically reversible way, for instance the most efficient thermal motor possible is one that uses a Carnot cycle. Most real-world engines use different, less efficient cycles like the Otto or Stirling cycle because they yield higher speeds or torque.

Losing the ability to reverse computations means increasing entropy and thus lower efficiency. Interestingly, there is a whole class of functional programming methods that is intrinsically reversible (because evaluating expressions without side effects is reversible).

The best explanations of the issues involved is in Richard Feynman's "Lectures on Computation", that show how thermodynamics constrain what is ultimately possible with a computer.

Re:Thermodynamics 101 (4, Insightful)

iggymanz (596061) | more than 10 years ago | (#7447678)

funny this topic has popped up again after I saw it featured in Scientific American over 10 years ago....the real problem is that no one wants to halve the number of useful gates on a chp in order to bulid all the extra circuitry required to reduce (of course, not eliminate, entropy still will increase though at lessened rate) the thermodynamic cost of "forgetting" data.

I attack instead the basic premise, that there is a shortage of energy, or that we must accept lower standard of life or lower capability in our machinery. What we DO need to do is get smarter about where we get our energy - instead of adding to net heat budget and pollution budget of earth getting really serious about solar energy (which might just mean making hydrocarbon fuel out of plant & suitable waste materials)

Are you kidding me? (0)

Anonymous Coward | more than 10 years ago | (#7447596)

Where are my cheap, reliable, and fast solid state hard drives?

And flying cars!!! I was promised flying cars!!!

Not exactly a "radical idea" ... (1)

Dlugar (124619) | more than 10 years ago | (#7447604)

The article mentions itself that this idea "date[s] back to the early 1960s" ... Feynman gave a lecture at some conference in Japan, I believe, in which he gave detailed explanations of his ideas for reversible logic gates, and the theoretical uses and limits for such machines. You can find it in the book The Pleasure of Finding Things Out [amazon.com] , which I have, or apparently also in Feynman Lectures on Computation [amazon.com] , which I don't have. I don't have either book on-hand to check out the exact date, but it was quite a while ago.

However, while it may not be particularly new or radical, it is quite interesting.


Dlugar

Future Energy Star Notice: (1)

farrellj (563) | more than 10 years ago | (#7447617)

This computer uses 100% recycled electrons. No electrons were destoryed or harmed by this computer.

'Splain somthin' to me... (aka. IANAEE, but...) (1)

OrbNobz (2505) | more than 10 years ago | (#7447625)

From the article:
"In theory, these oscillators could recapture most of the energy expended in a calculation and reuse it other calculations."
What the hell does this mean?
4(0100) + 3(0011) = 7(0111)
Ok, now, let's take that 0111 and use the bits for the answer to 7+8.
Is that really what they're saying?

"The concept is somewhat analogous to hybrid cars now on the market that take the energy generated during braking and recycle it into electricity used to power the car."
Ummm, no. The car analogy would work if we captured the waste heat thrown off, and converted it back to electricity. The concept here is that we don't waste the heat to begin with. This would be analogous to driving back to point A in reverse and reclaiming the fuel.

How could this possibly work?

- OrbNobz
I, for one, welcome our new reversible friends!!sdneirf elbisrever wen ruo emoclew ,eno rof ,I
The preceding statement took absolutely no energy to write.

Sounds like (1)

karlandtanya (601084) | more than 10 years ago | (#7447648)

..collaboration with this guy [timecube.com] would be productive.

Is PC power use really a big issue at this time? (1, Interesting)

Anonymous Coward | more than 10 years ago | (#7447655)

I don't know about AMD, but at least Via and Transmeta and I think Intel are already producing processors that can handle most any PC application including playing high resolution videos while running on around ten watts of power. That's not a terribly significant amount of power even compared to flourescent lighting.

I'm thinking these will all be made in Russia.... (1)

DeionXxX (261398) | more than 10 years ago | (#7447658)

These reversable computers must be Russian because I've heard on /. that:

In Soviet Russia computers use you.

-- D3X
NeoX3.com: The One site you'll ever need for XXX [neox3.com] .

Overstatement (0)

radicalskeptic (644346) | more than 10 years ago | (#7447662)

In fact, unless reversible computing is achieved, computer chips are expected to reach their maximum performance capabilities within the next three decades, effectively halting the rapid advances in speed that have driven the information technology revolution, Frank said. "Reversible computing is absolutely the only possible way to beat this limit," he said.

Uh, does anyone else thinks that's incredibly short sighted? Especially considering other technologies on the horizon (quantum computing, bilogical computing, networking technologies, etc). They all have their problems, but so does reversible computing. Who does he think he's fooling?

good bye thermodynamics!!! (0)

supercooled32 (722063) | more than 10 years ago | (#7447696)

I get it!!!

so all they need is to reverse the laws of entropy!!!

why had no one thought of that before?

this must be why these nanotechs are making the big bucks....

We already have reversible robots (1)

AtariAmarok (451306) | more than 10 years ago | (#7447699)

We already have reversible robots. [transformers.com] . Why not reversible computers?

"Apple Toast-Or! From G5 Power, to nice warm toast, back to G5 Power again!"

Are there other uses for MEMs (1)

aashenfe (558026) | more than 10 years ago | (#7447702)

I'm no physicist, but I was wondering, couldn't these mini electro-mechanical devices be a more efficient way to make electricity from heat.

If I remember correctly heat is manifest as molecular motion, or radiation.

So couldnt a small enough array of MEM's make electricity out of this molecular motion while cooling at the same time?

I'm thinking if this is the case, it could result in a lot of nice applications in the future.

For instance super fuel efficent electric generators, Freezers/ air conditioning that generates electricity, etc

Although this sounds like it would break some law of physics.

Stock Posturing (1)

MojoRilla (591502) | more than 10 years ago | (#7447718)

In fact, unless reversible computing is achieved, computer chips are expected to reach their maximum performance capabilities within the next three decades, effectively halting the rapid advances in speed that have driven the information technology revolution, Frank said. "Reversible computing is absolutely the only possible way to beat this limit," he said.
Anyone who is this emphatic about his own technology, and that it is the "only possible way" is trying to pump stock prices, plain and simple.

All technologies have a serious risk of failure, and even sound technology might fail due to uncontrolable forces. And there is never just one way to accomplish anything.

Energy transfer (0)

Anonymous Coward | more than 10 years ago | (#7447719)

In terms of energy transfer, where's the gain compared to the fact that I save some money on heating my apartment this time of the year? I mean, the hot air coming out of the computer must be saving me some money, right?

More about 'Reversible' Computers (1)

rpiquepa (644694) | more than 10 years ago | (#7447730)

I commented on this University of Florida news release a week ago on my blog [weblogs.com] . Not only you'll see more references and details than on the news release, but you'll also read comments by Michael Frank, the UF assistant professor behind this research effort.

a practical use (2, Funny)

MrLint (519792) | more than 10 years ago | (#7447745)

Imagine a computer that ran on heat and got colder the more you used it.. then i could pay video games and have ice cold beer.

Oh thats not what they mean by reversible? Damn

Quick! (0)

Anonymous Coward | more than 10 years ago | (#7447755)

Quick! Somebody write a method to Recycle memory instead of GarbageCollect! This could be BIG!
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