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Why CPUs aren't getting any faster (2010)

neona 12y ago
I hope we see an increase in real software parallelism, since that's the only real way out of this for the foreseeable future. Tacking on more cores is still an option we have, we're just having trouble using them right now in many contexts. In the longer term, we'll hopefully see advancements that let us fundamentally change how logic processors are constructed, such as possibly photonic logic chips. Only a major shift will let us break through the current single-thread performance wall.
- AshleysBrain 12y ago
  New architectures like the Mill (http://millcomputing.com/ http://millcomputing.com/) could provide alternative ways to a breakthrough increase in performance. On the software side, I've always understood browsers are pretty good at parallelism, which is a pretty major platform that gets performance benefits. That could also extend even further with projects like Mozilla's Servo (https://github.com/mozilla/servo https://github.com/mozilla/servo), a browser engine built from the ground up with parallelism in mind.
  - willvarfar 12y ago
    Yet JavaScript is fundamentally single threaded by design...
    - demallien 12y ago
      Take a look at Chromium as an example. Every tab gets it's own process. The GPU gets it's own process. Every plugin object gets its own process. Page loading is done in a separate process. Web workers run in a separate process. Chromium will happily eat up every core your CPU has to offer.
      - pcwalton 12y ago
        If you're running multiple tabs at the same time and actually interacting with both. But most of the time you're only laying out and rendering one page at a time; your browser actually only displays one tab at a time, after all.
    - AshleysBrain 12y ago
      I don't think that's actually true. The way it use asynchronous callbacks allows for lots of parallelism. For example creating a new image will cause it to download the image off the network and decompress it in parallel to executing Javascript, and then when done it fires the 'onload' handler. That's much more parallel-by-design than something like C++.
      - pcwalton 12y ago
        Unfortunately you can't actually run those callbacks in parallel, because of JavaScript's run to completion model. The work we're doing with PJs, however, attempts to fix this problem :)
higherpurpose 12y ago
Interesting that the article mentions SNB, because since then the gains in performance have been much smaller. SNB was the last "significant" gain in performance for Intel CPU's I'd say (+35 percent over previous generation). All of the new generations since then have gotten like 10 percent increase in IPC, at best, and Broadwell will probably get a max gain of +5 percent. To "hide" this, Intel has refocused its marketing on power consumption, where gains seem easier to achieve (for now), as well as other pure marketing tricks such as calling what used to be "Turbo Boost speed", the "normal speed". I've noticed for example recently a Bay Trail laptop being marketed at "2 Ghz", even though Bay Trail's base speed is much lower than that.
- zwegner 12y ago
  Depends on the application, of course. Haswell introduced some really cool new instructions (both the Bit Manipulation set as well as the Software Transactional Memory set). Don't have any numbers off-hand, but these can definitely speed up certain workloads.
  - supergauntlet 12y ago
    Apparently in specific workloads the move from AVX -> AVX2 was very substantial, though I can't seem to find the article that showed this.
    - vardump 12y ago
      The transition is more like from SSE2 -> AVX2, in integer workloads. AVX2 adds 256-bit wide integer instructions and gather-instruction. Gather does multiple loads in one instruction. AVX was just about floating point.
- Guvante 12y ago
  > as well as other pure marketing tricks such as calling what used to be "Turbo Boost speed", the "normal speed" I always found calling it turbo boost speed odd. During the majority of applications that exist today that is the speed you will get.
th3iedkid 12y ago
Weren't there walls back in the 90s?I would rather bet on a new tech leap than to go by federated designs at this stage.
- tedsanders 12y ago
  Yes, there were walls back in the 90s and yes, we managed to break through them. However, the walls we face today look much nastier. I concede that there's no way to know the future, but nonetheless I'd put my money on a sharply slower rate of improvement for CPUs. In the short term, it would be great if we had a breakthrough in x-ray power sources (for cheaper EUV lithography), a breakthrough in etch control (for vertical transistors), or a breakthrough in III-V materials (for a one-time mobility improvement). But long term, we need to find an alternative to the transistor. Perhaps spintronics, perhaps non-von Neumann architectures, who knows. But there is no way that a paradigm-changing redesign will be competitive with silicon in the next 10 years. Silicon has a humongous advantage in manufacturing, supply chain, know-how, scaled production, etc. Even if we find a better technology (and we haven't) it may still take decades to get there.
bluedino 12y ago
Additions to the instruction set can help out where raw GHz don't get things done. Another big improvement has been moving certain functions to hardware - Intel's Quicksync is a great example of this.
- carsongross 12y ago
  The problem is that these advancements are one-offs and are increasingly difficult to both create and adopt. There was a great paper I read on compiler optimizations (I was a language guy in college) that pointed out that compiler optimizations were responsible for maybe a 2x improvement in program speeds, whereas CPU improvements were responsible for 1000x. Almost all the singularity-type techno-optimism was based on a curve drawn during the amazingly magical part of CPU development: shrink the die, double the speed. We are now past that, although many techno-optimists are casting around for a reason it will continue.
  - Guvante 12y ago
    Honestly if we can get multi-core programming working we can probably keep it going. Although that is an enormous if.
    - carsongross 12y ago
      Most problems are not trivially parallelizable and, in any event, Amdahl curves look a lot different than the exponential curves used to argue for The Singularity. We may have to make due with what we've got. Which, thankfully, is quite a lot.
      - marcosdumay 12y ago
        Well, our brain has a single thread performance that is already many orders of magnitude smaller than our current CPUs. Any claim that Amdahl's law will forbid human-like inteligence must explain why that isn't a problem to us. Or, like you said, yep, we do have a lot.
      - 12y ago
trustfundbaby 12y ago
The article doesn't go into it in depth, but I think the answer is that chip makers hit a wall somewhere over 3Ghz range where it became difficult to ramp up cpu frequency without spending ridiculous sums on cooling the processor so it could operate properly (you'll notice that even now, the fastest intel chips come in at the 3.1-3.2 Ghz range ... theres a reason for that) I was big into building computers during the cpu race between AMD/Intel back in the late 90's early 2000's and the Intel Pentium 4 processor line is notable for pushing the envelope from the the high 2Ghz range all the way up to the 3.4Ghz and 3.6ghz (I still have a 3.4Ghz chip sitting in my home office ... those were the days!) Wikipedia does a great job of chronicling what happened with the Pentium 4 line here http://en.wikipedia.org/wiki/Pentium_4 http://en.wikipedia.org/wiki/Pentium_4 with hints to what I've just alluded to above "Overclocking early stepping Northwood cores yielded a startling phenomenon. While core voltage approaching 1.7 V and above would often allow substantial additional gains in overclocking headroom, the processor would slowly (over several months or even weeks) become more unstable over time with a degradation in maximum stable clock speed before dying and becoming totally unusable" It was after their failures with the brute force attempt at higher cpu cycles that Intel finally went a different way with initially the Pentium M line (code named Dothan and Banias) http://en.wikipedia.org/wiki/Pentium_M http://en.wikipedia.org/wiki/Pentium_M and eventually the Core duo/Core series that they've since built on.
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  - habitue 12y ago
    But comparing the same processor, higher clock speed means faster processing. And, to a lesser extent but still usefully, clock speed is a good indication of relative speed in the same processor line. Let's not totally throw the baby out with the bathwater, just because the processor speed on different CPU organizations is not 100% equivalent. It's very often times a good proxy.
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logicallee 12y ago
This is why CPUs aren't getting any faster: https://www.google.com/search?q=c+%2F+5+ghz https://www.google.com/search?q=c+%2F+5+ghz
- morenoh149 12y ago
  care to explain? I'm curious what you mean by that google search
  - michael_nielsen 12y ago
    It means signals can only propagate about 6 centimeters during a single CPU clock cycle. That makes accessing information off-chip difficult in a single cycle, since 6 centimeters is on the same order as the linear scale of most motherboards. This limit doesn't immediately impact computations that are carried out entirely on-chip. I expect that's the great majority of computations on today's CPUs, which typically have large caches. So I'm not sure the GP's explanation is correct, although it's certainly interesting.
    - lotsofmangos 12y ago
      As an explanation for why you cant get clock speed increases of the same order of magnitude as you could previously, without changing the entire technology, it would seem correct. 6cm now means that you only need to double twice to get to less than the die width. Also, electricity does not propagate through copper at c, but at between 40% and 90% of it, depending on the inductance and capacitance of the circuit, so you are looking at even less of an increase before you start running into some really thorny problems as not only are you running up against relativistic limitations, but different bits of your chip can be doing it at noticeably different times.
  - frakturfreund 12y ago
    Nothing can't travel faster than the speed of light – including Electric current. So in a hypothetic 5 gigahertz CPU, there couldn't be a path through the wires/transistors longer than 5.99584916 – otherwise, the end result couldn't be correctly determined. That's why CPU's got smaller and smaller. But since the transistor shrinking slows down, and Adders/Multiplyer/Register/Decoding Logic etc. all takes some time and length, it's harder to make a CPU with a shorter longest path.
exelius 12y ago
IMO CPUs aren't getting any faster because we don't really need them to be much faster. Now before the flames begin, let me caveat that as "We don't really need them to be much faster at single-threaded workloads." The article round-aboutly mentions this in the context of specialized CPUs, specifically GPUs: GPUs are basically hyper-concentrated thread runners. They're not very fast at running any single thread, but they have efficient shared memory and can run thousands of individual threads at once. For larger workloads, we've gotten a lot more efficient through cloud computing. An individual CPU in the cloud is really not any faster than it was 5 years ago; but the advances made in energy efficiency (aka heat) and miniaturization mean you can fit a lot more of them in a smaller space. While the technical hurdles to going faster are very real, I think we've built a technical infrastructure that's just not as reliant on the performance of any single piece of the system as it used to be. Therefore there is less demand for faster CPUs, when for many of the traditional "hard" computational workloads, more CPUs works almost as well and is a lot easier to scale than faster CPUs.
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  - exelius 12y ago
    I was more referring to the top of the line server CPUs (i.e. the fastest possible.) In laptops and mobile, they make a balance between power draw and CPU speed. Many of the advances in the last few years have not been on raw speed, but rather on how to draw less power. In many ways, this somewhat proves my original point: raw CPU speed is not as important in a laptop setup as portability and battery life. The products that CPUs are being used in are optimizing for battery life and heat dissipation, and using the fastest CPU available that fits within those criteria. And at the end of the day, I really don't think you'd notice the CPU speed boost without a benchmark score. Is it nice to have? Sure, why not. But I know the MacBook Pro I had in 2007 was fast enough to do whatever I wanted; anymore I only upgrade to get a better screen...
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philosophus 12y ago
I realize this article is from 2010, but it could have mentioned AMD, which does have a 5 GHz chip available now. It requires liquid cooling however.
- zurn 12y ago
  IBM beat that by a hair or two, 5 GHz POWER6 processors came out in in 2007. And the newer, faster POWER7 chips are clocked lower. Clock frequency != performance.
Spittie 12y ago
I personally have my own idea for that: Sure, we have hit many walls, but I don't think that's the main reason for the slow down in CPU development. I think it's mostly because the R&D moved from making the CPU faster for making the CPU consume less, to follow the Laptop/Mobile market (as everyone loves/hates to say, every year is the year of the death of the PC). Also we're at the point where most of the very-requesting software isn't bottlenecked by the CPU, or where you can just throw more cores at the problem and solve it. And also software is starting to leverage GPU acceleration, which gives an huge boost when usable. And GPUs are getting a lot faster every new generation.
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jokoon 12y ago
or "why it's more and more relevant to code with performance in mind, and consider minimalist designs"
- josho 12y ago
  In my experience a minimalist design often requires more effort behind the scenes. So, I don't see the two having any relationship. Just one of many possible examples, the minimalist ios7 interface has an embedded physics engine so that all the springy/sliding views feel natural to the user.
  - freehunter 12y ago
    But there's a difference between a minimalist design and a design that looks minimalist. A minimalist design wouldn't need a physics engine because the things that need the physics engine are glitz effects. iOS 7 merely looks minimalist.
    - josho 12y ago
      Yes, the parallax effect on the background image is glitz. I'd argue, however, that the physic's engine is not glitz, but rather makes the device easier to use, because when things work and feel as we expect it reduces the amount of mental effort we have to spend thinking about how to accomplish a task. E.g. when you can swipe a view to the side, and it 'feels' just like swiping a piece of paper to the side then you don't have to think about how to use the device, it all just makes sense. That's a smart design, minimalist in appearance, yet processor intensive.
      - jokoon 12y ago
        maybe we could introduce the concept of "resource minimalism"
  - jokoon 12y ago
    I think this feature is not minimalist at all. Smooth scrolling consumes a lot of battery and processing power. > In my experience a minimalist design often requires more effort behind the scenes. Why ? When I say minimalist I essentially means less useless fancy features. Minimalist focuses on the useful, not on the feeling, so it can leave more room for other new features. The iPhone has a power of a 1995-2000 full fledged desktop PC or maybe more, yet it's using a lithium battery and it's 1cm thick. This applies to all hardware: it's not worth it anymore to invest into new hardware if you're unable to exploit current hardware to their full potential. You can throw money at chip technology, but at some point you also have to try throwing money at software and OS developers. Computers have always been about software, not hardware.
delroth 12y ago
CPUs are getting faster. Sandy Bridge is a 15-20% IPC improvement on Nehalem for some heavily integer and memory access based workloads. On the same workloads, Haswell is another 15-20% IPC improvement on Sandy Bridge. I work on the Dolphin Emulator (https://dolphin-emu.org/ https://dolphin-emu.org/) which is a very CPU intensive program (emulates a 730MHz PowerPC core, plus a GPU, plus a DSP, all of that in realtime). We try and track CPU improvements to provide our users with proper recommandations on what hardware to go for. Here are the results of a CPU benchmark based on our software: https://docs.google.com/spreadsheet/ccc?key=0AunYlOAfGABxdFQ0UzJyTFAxbzZhYWtGcGwySlRFa1E#gid=0 https://docs.google.com/spreadsheet/ccc?key=0AunYlOAfGABxdFQ...
- twoodfin 12y ago
  Given that we seem to be hitting the practical limit on CPU frequencies, it's interesting to speculate on what kind of (single thread) IPC headroom is still available. You can model those IPC limitations by assuming a CPU with unlimited registers, unlimited functional units, a perfect branch predictor, etc. and seeing how much ILP you can extract from benchmark code. Tighten the CPU's constraints and you get a sense of which capabilities are most valuable. Wall 1991[1] is the classic paper, AFAIK, and saw a limit with "quite ambitious" (for 1991) imagined future hardware at around 5-7 IPC in a 'median' benchmark. I'd be interested to hear how close Intel is getting and whether anyone's updated that result. [1] http://www.eecs.harvard.edu/~dbrooks/cs146-spring2004/wall-ilp.pdf http://www.eecs.harvard.edu/~dbrooks/cs146-spring2004/wall-i...
zwegner 12y ago
The article doesn't really seem to answer the question the title says it does. Of course there's the well-known reasons, nonlinearity of power vs frequency scaling, diminishing returns in hardware design, etc. But there are others that we don't hear so much about. Hardware design is still in pretty nascent stage, technology-wise. The languages used (say SystemC or Verilog) offer very little high-level abstraction, and the simulation tools suck. Sections of the CPU are still typically designed in isolation in an ad-hoc way, using barely any measurements, and rarely on anything more than a few small kernels. Excel is about the most statistically advanced tool used in this. Of course, CPUs are hugely intertwined and complicated beasts, and the optimal values of parameters such as register file sizes, number of reservation stations, cache latency, decode width, whatever, are all interconnected. As long as design teams only focus on their one little portion of the chip, without any overarching goal of global optimization, we're leaving a ton of performance on the table. And for that matter, so is software/compiler design. The software people have just been treating hardware as a fixed target they have no control over, trusting that it will keep improving. That makes us lazy, and our software becomes more and more slow, by design (The Great Moore's Law Compensator if you will, also known as https://en.wikipedia.org/wiki/Wirth%27s_law https://en.wikipedia.org/wiki/Wirth%27s_law). The same problems we see in hardware design, huge numbers of deeply intertwined parameters, also applies to software/compiler design. We're still writing in C++ for performance code, for chrissakes. And even beyond that, the parameters in software and hardware are deeply intertwined with each other. To optimize hardware parameters, you need to make lots of measurements of representative software workloads. But where do those come from, and how are they compiled? Compiler writers have the liberty to change the way code is compiled to optimize performance on a specific chip (even if this isn't done so much in practice). To get an actually representative measurement of hardware, these compiler changes need to be taken into account. Ideally, you'd be able to tune parameters at all layers of the stack, and design software and hardware together as one entity. That is, make a hardware change, then do lots of compiler changes to optimize for that particular hardware instantiation. This needs to be automated, easy to extend, and super-duper fast, to try all of the zillions of possibilities we're not touching at the moment. There's even "crazy" possibilities like moving functionality across the hardware/software barrier. Of course it's a difficult problem, but we've made almost zero progress on it. Backwards compatibility is another reason. New instructions get added regularly, but those are only for cases where big gains are achieved in important workloads. For the most part, CPU designers want improvements that work without a recompile, because that's what most businesses/consumers want. One can envision a software ecosystem that this wouldn't be such a problem for, but instead we have people still running IE6/WinXP/etc. Software can move at a glacial pace, and hardware needs to accommodate it. But this of course also enables this awfully slow pace of software progress.
snarfy 12y ago
Grace Harper explains it best: http://www.youtube.com/watch?v=JEpsKnWZrJ8 http://www.youtube.com/watch?v=JEpsKnWZrJ8
ufmace 12y ago
I'm curious if anyone here has any perspective on how close we are to absolute physical limits in CPU design. Last I heard, we're getting pretty close to dealing with quantum issues due to how small the transistor and connection size is getting, the frequency of light we need to do the etching, etc. I wonder if anybody knows how close we are to hitting hard limits in various categories. Surely, we'll hit some eventually, and I wonder what happens then.
- marcosdumay 12y ago
  Charge carriers tunneling through the insulating barrier of MOS-FETs are a problem for a few years already. The good news is that it reduces exponentialy with tension and insulator thikness, thus it can be worked around. Dopped areas on silicon transistors have a minimum diameter around 10nm, that's the uncertainty about the position of charge carriers. Features a bit smaller than that will probably work, but much smaller ones won't. That said, we are still far from the ultimate limits on CPU design. Those limits above apply to CMOS CPUs made of silicon what, despite describing all of the currently produced ones, is only one among many possibilities.
- noir_lord 12y ago
  > Surely, we'll hit some eventually, and I wonder what happens then. Probably some radical break through using some basic physics principle some guys worked on 30 years ago and left in a library somewhere ;).
zokier 12y ago
The power wall theory is bit odd though. Why are modern Intel desktop CPUs limited to so low power budgets? Ivy bridges were just 77W (TDP), and now Haswells are apparently 65-84W. Desktop platforms should be able to handle far more power, at least in the 100-150 watt range. Meanwhile desktop GPUs are hitting 200-300 watt TDPs regularly, with far more limited cooling systems. Why isn't Intel able (or willing) to push the power envelope higher in desktops?
- wmf 12y ago
  Maybe because Intel "desktop" processors are just laptop processors in slightly different packaging. Or maybe they want to push more customers into the more expensive -E segment.
  - wtallis 12y ago
    But even the enterprise parts only have higher TDPs due to higher core counts - the cores themselves are the same as the consumer desktop parts, with a bit more cache thrown in and some transceivers to help scalability to even higher core counts that we don't want. Nobody is trying to design the fastest quad-core processor, let alone dual-core or single-core. No one is willing to commercialize a chip that is 10% faster at single-threaded tasks when it will be a fourth the speed at highly-threaded tasks, especially when the processor can self-overclock one core when it's the only one in use, thereby offsetting some of the core-count tradeoff.
  - awalton 12y ago
    They're different chips - the laptop chips get much better perf/watt than the desktop components which are comparatively sloppy. That power management hardware is actually somewhat expensive technologically. It really has more to do with the customers. The people buying these chips by the thousands are Enterprise Desktops, and keeping power bills down is their #1 goal. The customers don't buy GPUs in these machines either, they expect Intel's to be "good enough." Unfortunately, consumer desktop purchases are basically a rounding error to Intel's multibillion dollar balance sheets, so they don't build parts for that segment. Instead, they blow some fuses on their enterprise parts and sell them as "Extreme Performance", "Enthusiast Desktop" or whatever other euphemism they want to use for "overclockable" these days.
akuma73 12y ago
The end of Dennard scaling is the root-cause. This is causing power density to stop scaling with smaller transistors and will ultimately be the end of Moore's law. http://research.microsoft.com/en-us/events/fs2013/doug-burger_beastfrombelow.pdf http://research.microsoft.com/en-us/events/fs2013/doug-burge...
- tedsanders 12y ago
  Hmm, I don't think so. I'd say the end of Dennard scaling is why frequencies stopped going up around 2003. What's killing Moore's law now is not Dennard's law ending, but the increasing price of lithography technologies. Right now we face the unpalatable choice between quadruple patterning (very expensive) and EUV (also very expensive). The industry is between a rock and hard place.

neona 12y ago

I hope we see an increase in real software parallelism, since that's the only real way out of this for the foreseeable future. Tacking on more cores is still an option we have, we're just having trouble using them right now in many contexts. In the longer term, we'll hopefully see advancements that let us fundamentally change how logic processors are constructed, such as possibly photonic logic chips. Only a major shift will let us break through the current single-thread performance wall.

AshleysBrain 12y ago
New architectures like the Mill (http://millcomputing.com/ http://millcomputing.com/) could provide alternative ways to a breakthrough increase in performance. On the software side, I've always understood browsers are pretty good at parallelism, which is a pretty major platform that gets performance benefits. That could also extend even further with projects like Mozilla's Servo (https://github.com/mozilla/servo https://github.com/mozilla/servo), a browser engine built from the ground up with parallelism in mind.
- willvarfar 12y ago
  Yet JavaScript is fundamentally single threaded by design...
  - demallien 12y ago
    Take a look at Chromium as an example. Every tab gets it's own process. The GPU gets it's own process. Every plugin object gets its own process. Page loading is done in a separate process. Web workers run in a separate process. Chromium will happily eat up every core your CPU has to offer.
    - pcwalton 12y ago
      If you're running multiple tabs at the same time and actually interacting with both. But most of the time you're only laying out and rendering one page at a time; your browser actually only displays one tab at a time, after all.
  - AshleysBrain 12y ago
    I don't think that's actually true. The way it use asynchronous callbacks allows for lots of parallelism. For example creating a new image will cause it to download the image off the network and decompress it in parallel to executing Javascript, and then when done it fires the 'onload' handler. That's much more parallel-by-design than something like C++.
    - pcwalton 12y ago
      Unfortunately you can't actually run those callbacks in parallel, because of JavaScript's run to completion model. The work we're doing with PJs, however, attempts to fix this problem :)

higherpurpose 12y ago

Interesting that the article mentions SNB, because since then the gains in performance have been much smaller. SNB was the last "significant" gain in performance for Intel CPU's I'd say (+35 percent over previous generation). All of the new generations since then have gotten like 10 percent increase in IPC, at best, and Broadwell will probably get a max gain of +5 percent. To "hide" this, Intel has refocused its marketing on power consumption, where gains seem easier to achieve (for now), as well as other pure marketing tricks such as calling what used to be "Turbo Boost speed", the "normal speed". I've noticed for example recently a Bay Trail laptop being marketed at "2 Ghz", even though Bay Trail's base speed is much lower than that.

zwegner 12y ago
Depends on the application, of course. Haswell introduced some really cool new instructions (both the Bit Manipulation set as well as the Software Transactional Memory set). Don't have any numbers off-hand, but these can definitely speed up certain workloads.
- supergauntlet 12y ago
  Apparently in specific workloads the move from AVX -> AVX2 was very substantial, though I can't seem to find the article that showed this.
  - vardump 12y ago
    The transition is more like from SSE2 -> AVX2, in integer workloads. AVX2 adds 256-bit wide integer instructions and gather-instruction. Gather does multiple loads in one instruction. AVX was just about floating point.
Guvante 12y ago
> as well as other pure marketing tricks such as calling what used to be "Turbo Boost speed", the "normal speed" I always found calling it turbo boost speed odd. During the majority of applications that exist today that is the speed you will get.

th3iedkid 12y ago

Weren't there walls back in the 90s?I would rather bet on a new tech leap than to go by federated designs at this stage.

tedsanders 12y ago
Yes, there were walls back in the 90s and yes, we managed to break through them. However, the walls we face today look much nastier. I concede that there's no way to know the future, but nonetheless I'd put my money on a sharply slower rate of improvement for CPUs. In the short term, it would be great if we had a breakthrough in x-ray power sources (for cheaper EUV lithography), a breakthrough in etch control (for vertical transistors), or a breakthrough in III-V materials (for a one-time mobility improvement). But long term, we need to find an alternative to the transistor. Perhaps spintronics, perhaps non-von Neumann architectures, who knows. But there is no way that a paradigm-changing redesign will be competitive with silicon in the next 10 years. Silicon has a humongous advantage in manufacturing, supply chain, know-how, scaled production, etc. Even if we find a better technology (and we haven't) it may still take decades to get there.

bluedino 12y ago

Additions to the instruction set can help out where raw GHz don't get things done. Another big improvement has been moving certain functions to hardware - Intel's Quicksync is a great example of this.

carsongross 12y ago
The problem is that these advancements are one-offs and are increasingly difficult to both create and adopt. There was a great paper I read on compiler optimizations (I was a language guy in college) that pointed out that compiler optimizations were responsible for maybe a 2x improvement in program speeds, whereas CPU improvements were responsible for 1000x. Almost all the singularity-type techno-optimism was based on a curve drawn during the amazingly magical part of CPU development: shrink the die, double the speed. We are now past that, although many techno-optimists are casting around for a reason it will continue.
- Guvante 12y ago
  Honestly if we can get multi-core programming working we can probably keep it going. Although that is an enormous if.
  - carsongross 12y ago
    Most problems are not trivially parallelizable and, in any event, Amdahl curves look a lot different than the exponential curves used to argue for The Singularity. We may have to make due with what we've got. Which, thankfully, is quite a lot.
    - marcosdumay 12y ago
      Well, our brain has a single thread performance that is already many orders of magnitude smaller than our current CPUs. Any claim that Amdahl's law will forbid human-like inteligence must explain why that isn't a problem to us. Or, like you said, yep, we do have a lot.
    - 12y ago

trustfundbaby 12y ago

The article doesn't go into it in depth, but I think the answer is that chip makers hit a wall somewhere over 3Ghz range where it became difficult to ramp up cpu frequency without spending ridiculous sums on cooling the processor so it could operate properly (you'll notice that even now, the fastest intel chips come in at the 3.1-3.2 Ghz range ... theres a reason for that) I was big into building computers during the cpu race between AMD/Intel back in the late 90's early 2000's and the Intel Pentium 4 processor line is notable for pushing the envelope from the the high 2Ghz range all the way up to the 3.4Ghz and 3.6ghz (I still have a 3.4Ghz chip sitting in my home office ... those were the days!) Wikipedia does a great job of chronicling what happened with the Pentium 4 line here http://en.wikipedia.org/wiki/Pentium_4 http://en.wikipedia.org/wiki/Pentium_4 with hints to what I've just alluded to above "Overclocking early stepping Northwood cores yielded a startling phenomenon. While core voltage approaching 1.7 V and above would often allow substantial additional gains in overclocking headroom, the processor would slowly (over several months or even weeks) become more unstable over time with a degradation in maximum stable clock speed before dying and becoming totally unusable" It was after their failures with the brute force attempt at higher cpu cycles that Intel finally went a different way with initially the Pentium M line (code named Dothan and Banias) http://en.wikipedia.org/wiki/Pentium_M http://en.wikipedia.org/wiki/Pentium_M and eventually the Core duo/Core series that they've since built on.

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- habitue 12y ago
  But comparing the same processor, higher clock speed means faster processing. And, to a lesser extent but still usefully, clock speed is a good indication of relative speed in the same processor line. Let's not totally throw the baby out with the bathwater, just because the processor speed on different CPU organizations is not 100% equivalent. It's very often times a good proxy.
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logicallee 12y ago

This is why CPUs aren't getting any faster: https://www.google.com/search?q=c+%2F+5+ghz https://www.google.com/search?q=c+%2F+5+ghz

morenoh149 12y ago
care to explain? I'm curious what you mean by that google search
- michael_nielsen 12y ago
  It means signals can only propagate about 6 centimeters during a single CPU clock cycle. That makes accessing information off-chip difficult in a single cycle, since 6 centimeters is on the same order as the linear scale of most motherboards. This limit doesn't immediately impact computations that are carried out entirely on-chip. I expect that's the great majority of computations on today's CPUs, which typically have large caches. So I'm not sure the GP's explanation is correct, although it's certainly interesting.
  - lotsofmangos 12y ago
    As an explanation for why you cant get clock speed increases of the same order of magnitude as you could previously, without changing the entire technology, it would seem correct. 6cm now means that you only need to double twice to get to less than the die width. Also, electricity does not propagate through copper at c, but at between 40% and 90% of it, depending on the inductance and capacitance of the circuit, so you are looking at even less of an increase before you start running into some really thorny problems as not only are you running up against relativistic limitations, but different bits of your chip can be doing it at noticeably different times.
- frakturfreund 12y ago
  Nothing can't travel faster than the speed of light – including Electric current. So in a hypothetic 5 gigahertz CPU, there couldn't be a path through the wires/transistors longer than 5.99584916 – otherwise, the end result couldn't be correctly determined. That's why CPU's got smaller and smaller. But since the transistor shrinking slows down, and Adders/Multiplyer/Register/Decoding Logic etc. all takes some time and length, it's harder to make a CPU with a shorter longest path.

exelius 12y ago

IMO CPUs aren't getting any faster because we don't really need them to be much faster. Now before the flames begin, let me caveat that as "We don't really need them to be much faster at single-threaded workloads." The article round-aboutly mentions this in the context of specialized CPUs, specifically GPUs: GPUs are basically hyper-concentrated thread runners. They're not very fast at running any single thread, but they have efficient shared memory and can run thousands of individual threads at once. For larger workloads, we've gotten a lot more efficient through cloud computing. An individual CPU in the cloud is really not any faster than it was 5 years ago; but the advances made in energy efficiency (aka heat) and miniaturization mean you can fit a lot more of them in a smaller space. While the technical hurdles to going faster are very real, I think we've built a technical infrastructure that's just not as reliant on the performance of any single piece of the system as it used to be. Therefore there is less demand for faster CPUs, when for many of the traditional "hard" computational workloads, more CPUs works almost as well and is a lot easier to scale than faster CPUs.

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- exelius 12y ago
  I was more referring to the top of the line server CPUs (i.e. the fastest possible.) In laptops and mobile, they make a balance between power draw and CPU speed. Many of the advances in the last few years have not been on raw speed, but rather on how to draw less power. In many ways, this somewhat proves my original point: raw CPU speed is not as important in a laptop setup as portability and battery life. The products that CPUs are being used in are optimizing for battery life and heat dissipation, and using the fastest CPU available that fits within those criteria. And at the end of the day, I really don't think you'd notice the CPU speed boost without a benchmark score. Is it nice to have? Sure, why not. But I know the MacBook Pro I had in 2007 was fast enough to do whatever I wanted; anymore I only upgrade to get a better screen...
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philosophus 12y ago

I realize this article is from 2010, but it could have mentioned AMD, which does have a 5 GHz chip available now. It requires liquid cooling however.

zurn 12y ago
IBM beat that by a hair or two, 5 GHz POWER6 processors came out in in 2007. And the newer, faster POWER7 chips are clocked lower. Clock frequency != performance.

Spittie 12y ago

I personally have my own idea for that: Sure, we have hit many walls, but I don't think that's the main reason for the slow down in CPU development. I think it's mostly because the R&D moved from making the CPU faster for making the CPU consume less, to follow the Laptop/Mobile market (as everyone loves/hates to say, every year is the year of the death of the PC). Also we're at the point where most of the very-requesting software isn't bottlenecked by the CPU, or where you can just throw more cores at the problem and solve it. And also software is starting to leverage GPU acceleration, which gives an huge boost when usable. And GPUs are getting a lot faster every new generation.

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jokoon 12y ago

or "why it's more and more relevant to code with performance in mind, and consider minimalist designs"

josho 12y ago
In my experience a minimalist design often requires more effort behind the scenes. So, I don't see the two having any relationship. Just one of many possible examples, the minimalist ios7 interface has an embedded physics engine so that all the springy/sliding views feel natural to the user.
- freehunter 12y ago
  But there's a difference between a minimalist design and a design that looks minimalist. A minimalist design wouldn't need a physics engine because the things that need the physics engine are glitz effects. iOS 7 merely looks minimalist.
  - josho 12y ago
    Yes, the parallax effect on the background image is glitz. I'd argue, however, that the physic's engine is not glitz, but rather makes the device easier to use, because when things work and feel as we expect it reduces the amount of mental effort we have to spend thinking about how to accomplish a task. E.g. when you can swipe a view to the side, and it 'feels' just like swiping a piece of paper to the side then you don't have to think about how to use the device, it all just makes sense. That's a smart design, minimalist in appearance, yet processor intensive.
    - jokoon 12y ago
      maybe we could introduce the concept of "resource minimalism"
- jokoon 12y ago
  I think this feature is not minimalist at all. Smooth scrolling consumes a lot of battery and processing power. > In my experience a minimalist design often requires more effort behind the scenes. Why ? When I say minimalist I essentially means less useless fancy features. Minimalist focuses on the useful, not on the feeling, so it can leave more room for other new features. The iPhone has a power of a 1995-2000 full fledged desktop PC or maybe more, yet it's using a lithium battery and it's 1cm thick. This applies to all hardware: it's not worth it anymore to invest into new hardware if you're unable to exploit current hardware to their full potential. You can throw money at chip technology, but at some point you also have to try throwing money at software and OS developers. Computers have always been about software, not hardware.

delroth 12y ago

CPUs are getting faster. Sandy Bridge is a 15-20% IPC improvement on Nehalem for some heavily integer and memory access based workloads. On the same workloads, Haswell is another 15-20% IPC improvement on Sandy Bridge. I work on the Dolphin Emulator (https://dolphin-emu.org/ https://dolphin-emu.org/) which is a very CPU intensive program (emulates a 730MHz PowerPC core, plus a GPU, plus a DSP, all of that in realtime). We try and track CPU improvements to provide our users with proper recommandations on what hardware to go for. Here are the results of a CPU benchmark based on our software: https://docs.google.com/spreadsheet/ccc?key=0AunYlOAfGABxdFQ0UzJyTFAxbzZhYWtGcGwySlRFa1E#gid=0 https://docs.google.com/spreadsheet/ccc?key=0AunYlOAfGABxdFQ...

twoodfin 12y ago
Given that we seem to be hitting the practical limit on CPU frequencies, it's interesting to speculate on what kind of (single thread) IPC headroom is still available. You can model those IPC limitations by assuming a CPU with unlimited registers, unlimited functional units, a perfect branch predictor, etc. and seeing how much ILP you can extract from benchmark code. Tighten the CPU's constraints and you get a sense of which capabilities are most valuable. Wall 1991[1] is the classic paper, AFAIK, and saw a limit with "quite ambitious" (for 1991) imagined future hardware at around 5-7 IPC in a 'median' benchmark. I'd be interested to hear how close Intel is getting and whether anyone's updated that result. [1] http://www.eecs.harvard.edu/~dbrooks/cs146-spring2004/wall-ilp.pdf http://www.eecs.harvard.edu/~dbrooks/cs146-spring2004/wall-i...

zwegner 12y ago

The article doesn't really seem to answer the question the title says it does. Of course there's the well-known reasons, nonlinearity of power vs frequency scaling, diminishing returns in hardware design, etc. But there are others that we don't hear so much about. Hardware design is still in pretty nascent stage, technology-wise. The languages used (say SystemC or Verilog) offer very little high-level abstraction, and the simulation tools suck. Sections of the CPU are still typically designed in isolation in an ad-hoc way, using barely any measurements, and rarely on anything more than a few small kernels. Excel is about the most statistically advanced tool used in this. Of course, CPUs are hugely intertwined and complicated beasts, and the optimal values of parameters such as register file sizes, number of reservation stations, cache latency, decode width, whatever, are all interconnected. As long as design teams only focus on their one little portion of the chip, without any overarching goal of global optimization, we're leaving a ton of performance on the table. And for that matter, so is software/compiler design. The software people have just been treating hardware as a fixed target they have no control over, trusting that it will keep improving. That makes us lazy, and our software becomes more and more slow, by design (The Great Moore's Law Compensator if you will, also known as https://en.wikipedia.org/wiki/Wirth%27s_law https://en.wikipedia.org/wiki/Wirth%27s_law). The same problems we see in hardware design, huge numbers of deeply intertwined parameters, also applies to software/compiler design. We're still writing in C++ for performance code, for chrissakes. And even beyond that, the parameters in software and hardware are deeply intertwined with each other. To optimize hardware parameters, you need to make lots of measurements of representative software workloads. But where do those come from, and how are they compiled? Compiler writers have the liberty to change the way code is compiled to optimize performance on a specific chip (even if this isn't done so much in practice). To get an actually representative measurement of hardware, these compiler changes need to be taken into account. Ideally, you'd be able to tune parameters at all layers of the stack, and design software and hardware together as one entity. That is, make a hardware change, then do lots of compiler changes to optimize for that particular hardware instantiation. This needs to be automated, easy to extend, and super-duper fast, to try all of the zillions of possibilities we're not touching at the moment. There's even "crazy" possibilities like moving functionality across the hardware/software barrier. Of course it's a difficult problem, but we've made almost zero progress on it. Backwards compatibility is another reason. New instructions get added regularly, but those are only for cases where big gains are achieved in important workloads. For the most part, CPU designers want improvements that work without a recompile, because that's what most businesses/consumers want. One can envision a software ecosystem that this wouldn't be such a problem for, but instead we have people still running IE6/WinXP/etc. Software can move at a glacial pace, and hardware needs to accommodate it. But this of course also enables this awfully slow pace of software progress.

snarfy 12y ago

Grace Harper explains it best: http://www.youtube.com/watch?v=JEpsKnWZrJ8 http://www.youtube.com/watch?v=JEpsKnWZrJ8

ufmace 12y ago

I'm curious if anyone here has any perspective on how close we are to absolute physical limits in CPU design. Last I heard, we're getting pretty close to dealing with quantum issues due to how small the transistor and connection size is getting, the frequency of light we need to do the etching, etc. I wonder if anybody knows how close we are to hitting hard limits in various categories. Surely, we'll hit some eventually, and I wonder what happens then.

marcosdumay 12y ago
Charge carriers tunneling through the insulating barrier of MOS-FETs are a problem for a few years already. The good news is that it reduces exponentialy with tension and insulator thikness, thus it can be worked around. Dopped areas on silicon transistors have a minimum diameter around 10nm, that's the uncertainty about the position of charge carriers. Features a bit smaller than that will probably work, but much smaller ones won't. That said, we are still far from the ultimate limits on CPU design. Those limits above apply to CMOS CPUs made of silicon what, despite describing all of the currently produced ones, is only one among many possibilities.
noir_lord 12y ago
> Surely, we'll hit some eventually, and I wonder what happens then. Probably some radical break through using some basic physics principle some guys worked on 30 years ago and left in a library somewhere ;).

zokier 12y ago

The power wall theory is bit odd though. Why are modern Intel desktop CPUs limited to so low power budgets? Ivy bridges were just 77W (TDP), and now Haswells are apparently 65-84W. Desktop platforms should be able to handle far more power, at least in the 100-150 watt range. Meanwhile desktop GPUs are hitting 200-300 watt TDPs regularly, with far more limited cooling systems. Why isn't Intel able (or willing) to push the power envelope higher in desktops?

wmf 12y ago
Maybe because Intel "desktop" processors are just laptop processors in slightly different packaging. Or maybe they want to push more customers into the more expensive -E segment.
- wtallis 12y ago
  But even the enterprise parts only have higher TDPs due to higher core counts - the cores themselves are the same as the consumer desktop parts, with a bit more cache thrown in and some transceivers to help scalability to even higher core counts that we don't want. Nobody is trying to design the fastest quad-core processor, let alone dual-core or single-core. No one is willing to commercialize a chip that is 10% faster at single-threaded tasks when it will be a fourth the speed at highly-threaded tasks, especially when the processor can self-overclock one core when it's the only one in use, thereby offsetting some of the core-count tradeoff.
- awalton 12y ago
  They're different chips - the laptop chips get much better perf/watt than the desktop components which are comparatively sloppy. That power management hardware is actually somewhat expensive technologically. It really has more to do with the customers. The people buying these chips by the thousands are Enterprise Desktops, and keeping power bills down is their #1 goal. The customers don't buy GPUs in these machines either, they expect Intel's to be "good enough." Unfortunately, consumer desktop purchases are basically a rounding error to Intel's multibillion dollar balance sheets, so they don't build parts for that segment. Instead, they blow some fuses on their enterprise parts and sell them as "Extreme Performance", "Enthusiast Desktop" or whatever other euphemism they want to use for "overclockable" these days.

akuma73 12y ago

The end of Dennard scaling is the root-cause. This is causing power density to stop scaling with smaller transistors and will ultimately be the end of Moore's law. http://research.microsoft.com/en-us/events/fs2013/doug-burger_beastfrombelow.pdf http://research.microsoft.com/en-us/events/fs2013/doug-burge...

tedsanders 12y ago
Hmm, I don't think so. I'd say the end of Dennard scaling is why frequencies stopped going up around 2003. What's killing Moore's law now is not Dennard's law ending, but the increasing price of lithography technologies. Right now we face the unpalatable choice between quadruple patterning (very expensive) and EUV (also very expensive). The industry is between a rock and hard place.