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AMD Says Power Efficiency Still Key

Posted by ryuzaki0 on from the teaser-trailers dept.

Larsonist writes to tell us that even though AMD's new architecture wont be released until mid-2007 they are still letting people in on what some of the new features will be. From the article: "While clock speeds have not been revealed, each of the four cores will integrate 64 KB L1 Cache and 512 KB L2 cache. The native quad-core architecture will also include a 2 MB shared L3 cache, which may increase in capacity over time. The processor will have a total of four Hypertransport links - up from three today - that provide a total bandwidth to outside devices of 5.2 GB/s. AMD is also thinking about integrating support for FB-DIMMs 'when appropriate.'"

46 of 167 comments (clear)

  1. Almost obligatory statement... by Pharmboy · · Score: 5, Interesting

    But will it run Vista? (j/k)

    Is Vista going to support 4 cores, or like XP Pro and 2k, limit it to 2 "cpus" so they can charge more for the server version?

    --
    Tequila: It's not just for breakfast anymore!
    1. Re:Almost obligatory statement... by adisakp · · Score: 4, Informative

      MS licensing is for currently for physical CPU's not for cores. Right now a dual xenon (two CPU's) counts as two CPU's in MS licensing terms but a dual-core (two CPU's within a single die or processor socket) is one CPU under MS licensing terms.

      In other words, MS counts sockets, not cores.

    2. Re:Almost obligatory statement... by Virtex · · Score: 2, Funny
      But will it run Vista?
      Sadly, no. By the time Vista comes out, AMD and the rest of the world will have long since moved beyond quad-core processors.
      --
      For every post, there is an equal and opposite re-post.
    3. Re:Almost obligatory statement... by Pharmboy · · Score: 3, Interesting

      If I remember right, there was some controversy with Oracle considering a dual core as two cpus, and they backed off. If we see 4 or more cores, the need for multiple sockets goes down, and I just wonder if MS will reconsider this licensing to prevent "lost revenue".

      --
      Tequila: It's not just for breakfast anymore!
    4. Re:Almost obligatory statement... by dfinster · · Score: 3, Insightful

      Really interesting question. For my entire career (since 1983), hardware has outrun software, and OS software in particular. This is a new and interesting twist. Extracting money from users based on "number of processors" or "processor power factor" (think Oracle) may become more difficult in a world of muti-core, multi-die, and multiple architecture.

      For example, which is worth more (none of these CPUs exist) - a quad CORE 2 or a eight core Athlon XP?

      I'd expect the eight-way to be better at some tasks that are easy to multi-thread, perhaps database servers. I'd expect the quad CORE 2 to be better at most general tasks, mostly because current OS and compilers aren't designed for multiple cores.

    5. Re:Almost obligatory statement... by Anonymous Coward · · Score: 5, Informative

      Microsoft will not charge per core anytime soon. They might have a dominating position on the desktop, but when it comes to servers, they're fighting tooth and nail to get a position of respectability, let alone dominance.

      So, let's look at the two markets seperately.

      Desktop, the users are likely to not care too much, provided the "Per core" cost is low enough. When we start seeing 4/8/16 core CPUs, a $10 per core fee will add up quick, but most home users will be using OEM copies and won't see that cost. Most business will have site licenses and won't care. But, some home users will, and some businesses will care, and they'll seriously consider alternatives (Maybe, maybe not switching). Microsoft would much rather "lose" money by not fleecing people, than have them even CONSIDER switching, so management's going to ditch the idea for desktops and workstations.

      Server market... they need any advantage they can get. They main competition is Solaris, BSD, and Linux. Linux and BSD are *free*, and Solaris has a bunch of good features which are pretty much Solaris only, even still. Charging per core would be suicide in this market, too.

      So, what market would charging per core be a good idea for Microsoft? None. Say what you will about their software writing abilities, but nobody should doubt their marketing prowess.

    6. Re:Almost obligatory statement... by gmack · · Score: 2, Interesting

      I'm going to guess not very well at first. With all 4 cores having the abillity to run at different clocks speeds I doubt this qualifies as SMP anymore.

      Most SMP code is tested on CPUs of equal clock speeds so odds are this is going to bring out all sorts of fun race conditions in Vista, Linux and *BSD and I'm personally not so sure I'm going to touch this until the resulting dust settles.

      I'm not saying it's a bad idea.. it looks like a good one but this will take time for the software to mature.

    7. Re:Almost obligatory statement... by cecil_turtle · · Score: 3, Interesting

      I agree that Microsoft (or likely anybody else) won't change to a per-core pricing model, but for different reasons. The point of per-CPU pricing is just to determine the market - the type of user/computer:

      1 CPU = most laptops and desktops, low end servers
      2 CPU = high-end workstations, average servers
      4 CPU = high-end servers

      As the number of cores ramp up, as you said to 4/8/16, then charging per core would be like charging per GHz or per L2 cache size - it doesn't make sense, adding cores will just be another way that new chips get faster than old ones. But the number of actual CPUs/sockets to define a specific market will likely stay the same for some time. Other than the Oracle debacle that grandparent poster mentioned, all per-core pricing theories have just been speculation. I can't imagine any company successfully pulling that off.

    8. Re:Almost obligatory statement... by maraist · · Score: 3, Informative

      Most SMP code is tested on CPUs of equal clock speeds

      You're kidding right? I can't imagine any software which depends on the timing of coperative CPUs.. MPI and general divide-and-qonquer work-clusters could care less about the performance level of peer threads/co-processes. Hell process interrupts due to pre-emptive multi-tasking is enough to guarantee lack of symmetry.

      Now perhaps you're referring to scheduling problems in the kernel.. I'm sure that AMD would be generous enough to provide kernel patches as are necessary.

      --
      -Michael
    9. Re:Almost obligatory statement... by eggoeater · · Score: 4, Informative
      but when it comes to servers, they're fighting tooth and nail to get a position of respectability, let alone dominance.
      Are you kidding?
      I work for a very LARGE bank. I guarentee you we have more boxes running MS Server 2003 than all others combined.
      We have some HPUX, IBM, and SUN sprinkled in there but several of the vendor apps I've worked with lately has dropped all support
      for SunOS and is now requiring Windows Server for their apps.
      We use to run Novel for our file servers but that was dropped for MS Active Directory.
      The next leading server OS we use is probably zOS. No Linux yet but I know the powers-that-be are looking at it.
      (BTW, I'm no MS fanboy, I'm just making a point.)

      I'm sure there are many industries in which MS does not have the majority of the server market but
      large financial groups are not among them.

      --
      $7.95/mo, 200 GB disk, 2TBxfer, MySQL, PHP, RoR.
    10. Re:Almost obligatory statement... by adisakp · · Score: 2, Informative

      SMP means the processors are similar (i.e. can run identical binary code). They do not need to run in lock-step synchonization to be SMP. Indeed, it is currently possible to halt a single processor in a dual processor system (two sockets) so a similar case already exists in current SMP systems.

    11. Re:Almost obligatory statement... by Nutria · · Score: 2, Funny
      we have more boxes running MS Server 2003 than all others combined.

      Is that because you need more Server 2k3 boxes to get the job done?

      --
      "I don't know, therefore Aliens" Wafflebox1
    12. Re:Almost obligatory statement... by eggoeater · · Score: 4, Informative
      I'm sorry, but how does your anecdotal evidence of a single company change the fact that the majority of servers are not Windows? Microsoft was recently celebrating the fact that they hit the 25% mark for server sales (for a single quarter), and last I checked, 25% wasn't even a plurality in the server market.
      I wasn't saying they have a majority overall, just in my company.
      I was giving an example to counter the GPs claim that MS doesn't have respectability in the server market.

      Not only do they have respectability, I see more and more vendors requiring them and most custom apps we write is on MS (desktop and server), although a lot of our web stuff is IBM (websphere, etc).
      I work in telecommunications; Aspect, Avaya, Cisco (not cisco routers/switches) have ALL migrated from other OSs to MS in the past 5 years for their server and desktop apps.

      Yes, Novel, Sun, HP, and IBM are huge in the server business. Except for IBM, they will steadily lose share to MS over time.
      One of the main reasons this hasn't happened faster (like in the desktop arena) is because there are a LOT of home-grown apps that companies have built over the past 15 years that still require a particular OS to use.
      At the bank I work for, we have a home-grown desktop app that is "critical". It was originally written for OS2. Around 1997 the team was forced to port it to MS windows NT.
      The conversion was brutal and it took them forever to get all the bugs worked out.
      Cut to 9 years later. WERE STILL USING THAT APP! (and no one is happy about it.)
      They've tried 4 times in the past 5 years to either have it rewritten or replaced with a vendor product, but every project has failed.
      It's so bloated and patched it's a nightmare to maintain, but even tougher to replace.


      Now apply that story to the thousands of custom server apps in thousands of companies around the world that only run on SunOS, HPUX, Novel, etc.
      The number of custom web apps alone that have been written on Sun servers could keep that company going another 20 years.
      We run a lot of MS server OS at work because we've been busy migrating stuff over the past 5 years. (a LOT of stuff.)

      So, my point is, MS Server OSs are not only respectable, but many large companies are actively moving towards them because they see it as streamlining. (Large companies like to be consistent and stick to "industry standards", even if it doesn't make good business sense.)
      MS knows it's going to take time; it's not like replacing a desktop OS.


      --
      $7.95/mo, 200 GB disk, 2TBxfer, MySQL, PHP, RoR.
    13. Re:Almost obligatory statement... by eggoeater · · Score: 3, Interesting
      Is that because you need more Server 2k3 boxes to get the job done?
      Outside of the obvious joke, this is actually true, but probably not for the reasons you think.

      Real reason: politics. One of the problems with server apps is that they tend to be "critical" to normal operations of the business.
      This means if you tell someone, "Hey, your server is under-utilized so were going to put this other groups app on there...",
      the shit is definitely going to start flying. (ex. "that server came out of my budget..." etc.)

      Ask anyone where I work (or probably where anyone works) and they would say that it would be the end of the world to have to share a server.
      In truth, it's all too easy for someone to mess up and bring a server to it's knees.
      The group I work in, we have probably 80 servers (yes, they all run MS), and none of them can be shared because it violates the SLA we have with Cisco. They won't support the app if anything else is running on the server.
      (Cant say I entirely blame them.)

      They solution to this problem is virtualization; I've been telling my co-workers that the future of servers is virtualization.
      Until we can really make it work politically, we'll be running racks and racks of servers that mostly run 90+ percent idle.

      --
      $7.95/mo, 200 GB disk, 2TBxfer, MySQL, PHP, RoR.
    14. Re:Almost obligatory statement... by be-fan · · Score: 2, Informative

      Symmetric doesn't really have any deeper implications. It just implies the processors are similar. There's no underlying implications about synchronization. When writing code for SMP machines, not only is it not possible to accidentally depend on the processors being synchronized, it's impossible to explicitly depend on synchronization.

      Spin-locks or not, cores running at different clockspeeds aren't going to expose any more race conditions than regular usage. Even on a current SMP system, the processors will almost always be asymetrically loaded, so threads of an app won't really see the two processors running at the same speed anyway.

      --
      A deep unwavering belief is a sure sign you're missing something...
    15. Re:Almost obligatory statement... by Anonymous Coward · · Score: 2, Insightful

      Poster of the post you originally replied to here... Read my post more carefully. I didn't say that their OS wasn't 'respectable', but that their POSITION wasn't respectable. Their overall position in the server market is abysmal, something like 10-15%. And, like a first year marketing student can tell you (And will. Oh god, they won't ever stop babbling...) mind share matters. When IT managers think "Server", they generally think UNIX, and will look at UNIX solutions first, (Unless it's something like an Active Directory or Exchange server). The market position they have simply isn't respectable. If it were, when the CTO was thinking "server", it wouldn't be "What type of UNIX" it would be at LEAST "Should I go with UNIX or Windows". This doesn't mean that there are no companies, or even industries, where that's not the case, but overall that's how the market stands.

    16. Re:Almost obligatory statement... by hackstraw · · Score: 3, Interesting

      "processor power factor" (think Oracle)

      I'm not sure if Oracle still does this, but they used to have almost voodoo math to figure out how much you owe oracle. It was something like X/CPU, then that value multiplied by a scale for the type of CPU (at the time RISC vs CISC), and then another multiplier by the amount of RAM on the box.

      When I heard that, I always suggested under specing the box and then silently upgrading it after the Oracle guys left. I believe the technical term is sliding scale which means the more you can afford, the more you will pay.

    17. Re:Almost obligatory statement... by jelle · · Score: 2, Insightful

      "and none of them can be shared because it violates the SLA we have with Cisco."

      But _that_ is not politics, it's because Cisco understands windows servers and how badly they handle more than one task.

      --
      --- Hindsight is 20/20, but walking backwards is not the answer.
    18. Re:Almost obligatory statement... by catacow · · Score: 5, Informative

      SMP means the processors are similar (i.e. can run identical binary code). They do not need to run in lock-step synchonization to be SMP.

      The Symmetric in SMP refers to the fact that each process can run the same tasks.In an assymmetric setup, there may be a processor dedicated to the kernel or other tasks.

      It most definitely has nothing to do with speed.

    19. Re:Almost obligatory statement... by pchan- · · Score: 3, Informative

      Now perhaps you're referring to scheduling problems in the kernel.. I'm sure that AMD would be generous enough to provide kernel patches as are necessary.

      I find that the two processors in my dual-core Athlon X2 run at slightly different speeds (according to AMD, this is expected). That in fact did cause the Linux kernel some problems, since it was trying to balance handling the interrupts between the two. The problem happened when the timer interrupt bounced between the two, as within an hour or two of startup their tick counts became significantly separated. This made the system clock start running forward at a rapid rate. A Linux patch fixed this issue. So I can definitively say that Linux does run on SMP cores at different speeds.

      I'm not sure how Windows will do it, but they'll probably figure it out if they haven't yet. The real challenge is a new scheduling algorithm for variable CPU capabilities (although we do have that to some extent with frequency scaling on single CPUs).

  2. Power control at the per core level by adisakp · · Score: 4, Informative

    The article is very light on details but the one picture implies power control at the core level. For example if core-1 is running a 100% workload and core-2 has a 50% workload, core-3 and core-4 can be halted resulting in a power load of only 45% the total 4-core max load.

    1. Re:Power control at the per core level by adisakp · · Score: 5, Informative

      25% per core at 100% capacity. a core at 50% capacity would be half 25% or 12.5%... 37.5% total.

      Mathematically that's what you'd expect but 50% CPU load doesn't mean 50% the power - it completely depends on what state a 50% load puts the CPU in (lowered clock or same clock / sleep-state during idle / etc). Plus you have to remember that a halted-state CPU still consumes more power than a CPU that is completely powered down. This is why it takes 45% rather than 37.5%. You can't apply such simple principals to power calculations.

    2. Re:Power control at the per core level by ashridah · · Score: 4, Informative

      It's definently possible. Make sure the 'Cool-n-Quiet' junk is enabled in the bios on any recent AMDx2 system, and install powernowd or something similar under linux.

      My cpu speeds idle at around 1GHz, and then spring back up to 2.4GHz when under load, then slowly drop back to 1GHz when not in use. Independently, I might add.

  3. But will it... by corychristison · · Score: 3, Insightful

    ... run OS/2?

    Joking aside, lately I've been pondering AMD's next move in the everlasting Intel vs. AMD chess game.

    I'm here for hoping they can pull ahead again and force Intel to do the same.
    Always Remember: competition is good!

  4. Amazing by Urtica+dioica · · Score: 2, Funny

    ...they are still letting people in on what some of the new features will be.

    A company announcing upcoming features in order to create hype for their product? Who'd have thought of that.

  5. Biggest way for AMD to save power by Aaron+England · · Score: 4, Insightful

    is to reduce the distance between their transistors from 90nm to 65. Intel started shipping their 65nm chips nearly a year ago (OCT 2005), while AMD has yet to ship any. AMD isn't expected to be fully converted to the 65nm process until mid-2007, and by then Intel is expected to start shipping their 45nm chips. AMD is playing catch-up these days and it's hurting them bad.

    1. Re:Biggest way for AMD to save power by Anonymous Coward · · Score: 2, Interesting

      Intel have publically stated that they will not be shipping 45nm chips until 2008.

      Intel shipped a few 65nm processors in 2005, but didn't really get started until 2006, and full conversion might not have happened yet, although all the important plants should have migrated by now.

      AMD have been behind on the process node, but that's not the only issue when it comes to making chips, although it is the most major. SS + SOI are other technologies that AMD is far ahead of Intel on, and they help reduce power significantly - hence AMD's low power 90nm processors compared to Intel's 90nm, and even Intel's 65nm P4s, and AMD aren't doing too badly in terms of performance/Watt right now either.

    2. Re:Biggest way for AMD to save power by Aaron+England · · Score: 4, Informative
      Intel have publically stated that they will not be shipping 45nm chips until 2008.

      Nah. Here's what Intel's 45nm page says: This important milestone demonstrates that we are on track for 2007 to manufacture chips on 300mm wafers using the new 45nm (P1266) process, in accordance with Moore's Law.

      Intel shipped a few 65nm processors in 2005, but didn't really get started until 2006, and full conversion might not have happened yet, although all the important plants should have migrated by now.

      Even if true, AMD has yet to ship a SINGLE 65nm processor. By this measure alone, I'd say the claim that they are a year behind is quite adequete. But by the speed at which AMD is producing fab plants, I'd argue that they are or soon will be an entire chip generation behind.

      AMD have been behind on the process node, but that's not the only issue when it comes to making chips, although it is the most major. SS + SOI are other technologies that AMD is far ahead of Intel on, and they help reduce power significantly - hence AMD's low power 90nm processors compared to Intel's 90nm, and even Intel's 65nm P4s, and AMD aren't doing too badly in terms of performance/Watt right now either.

      Traditionally Intel has won the absolute performance title. As you said yourself it is the biggest factor when it comes to performance/Watt statistics. If been following any of the Core 2 Duo reviews, Intel is now dominating in that arena too.

  6. it's better actually by r00t · · Score: 3, Informative

    AMD now provides a TSC (cycle counter) that doesn't vary in speed when the core speed changes. This greatly helps with timekeeping.

    As for race conditions: that is pretty well taken care of already. SGI has Linux on a 2048-way system now.

    1. Re:it's better actually by gmack · · Score: 2, Interesting

      But were the 2048 way systems running at different clock speeds? Or rather were the processors in each node running at different clock speeds? Last time I saw someone on linux-kernel mismatch processors it brought all sorts of interesting issues out.

    2. Re:it's better actually by Jah-Wren+Ryel · · Score: 2, Informative

      But were the 2048 way systems running at different clock speeds?

      Different clock speeds should not present much of a problem. In terms of performance it should be a non-issue - right now you can get variable performance out of the same code depending on other factors like memory contention, cache pollution by other processes, etc so if a cycle takes 1.00ns or 0.50ns isn't going to be anything new.

      Only the scheduler is going to care about frequency differences, and considering that we already have the ability to dynamically vary frequency on current systems (intel speedstep, amd's cool-and-quiet) presumably the scheduler already knows how to handle variations in clock frequency - it probably uses a counter/interrupt-generator that is not affected by varying the clock.

      Last time I saw someone on linux-kernel mismatch processors it brought all sorts of interesting issues out.

      I'm going to guess that by "mismatch processors" there was more to it than just clock frequency. Probably at least cache size and type, maybe TLB size, and probably a bunch of similar minutae too. It's likely the kernel makes some assumptions about those kinds of characteristics, but they aren't likely to vary on the new AMD chips in the way they could with different models of chips in the same system.

      --
      When information is power, privacy is freedom.
  7. Power is always key by bblboy54 · · Score: 5, Informative

    Well, at least if you are in a data center.

    There are two huge concerns in a typical data center enviornment: Heat and Power. These two areas are key because of the density of servers today. We're cramming so much processing and storage into 48U that people 10 years ago couldnt have even dreamed of even existing. Delivering enough power to run 48 servers can be difficult if each server is pulling 4 amps each (thats 192 amps). Considering most circuits are 20 or 30amps, thats alot of circuits to fit in one rack.

    This was always the biggest reason why Dell servers were not as popular with the companies that I have worked with. Quite simply, AMD was kicking Intel's ass with heat and power. I heard many people say they'd start ordering Dell servers by the pallet if they sold AMD processors (looks like they finally listened).

  8. I don't get the point of this by Sloppy · · Score: 3, Interesting

    I'm sceptical that this technique will be very useful. (Of course, AMD is full of smart people and I'm just some net.moron.) I don't think it will be very common for the load on a 4-core processor to be somewhere the middle like 1.5. It's either going to be mostly idle (load close to 0) so you might as well power down the whole chip, or going full blast with the load as high as I think will give me the most throughput. For example, when compiling (and that's when I wish I had more cores) I'm gonna "make -j n" and my load is going to be about n, and that number is going to be chosen to be one more than the number of cores I have (or something like that). If I have a 4-core machine, do you think I'm going to make -j 2? No way.

    I can't think of many situations where I would have one core running at 100% and another at 50% and the others idle, for any significant length of time. I can imagine a desktop user clicking on something and maybe for a few milliseconds that load is somewhere around that, but then the work gets done and you're idling again. Or the user asked it to do something "hard" so all cores are near 100% (except maybe while waiting for I/O) for a "long" time.

    Am I wrong? What kinds of things does your computer work on, which are a little parallelizable but not very much?

    --
    As copyright owner of this comment, I authorize everyone to defeat any technological measure which limits access to it.
    1. Re:I don't get the point of this by Mr.+Hankey · · Score: 3, Interesting

      One of my computers (well, 'one' and 'my' being relative terms in this case) is a 40 node cluster, completely SMP with some of the newer nodes being dual core as well. Often they're fully utilized or more, imagine a 5.00+ loadavg per node weeks on end. When a job is winding down though, the remainder of the jobs will probably finish up one at a time and you often have a few CPUs with just one job running for a few days. It's good for the electric bill to allow the CPU cores to power down.

      Another of my computers is basically used to play games. Most games don't seem to do much on the SMP side, so I doubt it would much matter how many cores there were as far as the game's concerned. They do tend to peak one CPU pretty much all the time though, while another core might end up servicing OS calls. Again, it couldn't hurt to let those sleeping processors/cores power down while they're not doing much of anything.

      --
      GPL: Free as in will
    2. Re:I don't get the point of this by Jeremi · · Score: 2, Interesting
      Am I wrong? What kinds of things does your computer work on, which are a little parallelizable but not very much?


      How about games and media playback? In those applications, you have X amount of work that needs to be done every (say) 33ms... there might be more work to do than one core can handle, but not so much that you need all 4 cores.

      --


      I don't care if it's 90,000 hectares. That lake was not my doing.
    3. Re:I don't get the point of this by Alkivar · · Score: 2, Interesting

      Games.... at least for the moment. Very few companies producing games are parallelizing their code. I can see the 100% being the core the game is running on, and the 50% core being the overhead of the interaction between the CPU an GPU. At least thats the only scenario I can currently think of...

  9. OpenGL equivalent for Ray Tracing by ErroneousBee · · Score: 2, Interesting

    How does this tally with a previous story about multi-core architectures being ideal for realtime ray-tracing in games? Is anyone working on a Ray-Tracing evuivalent of OpenGL?

    --
    **TODO** Steal someone elses sig.
  10. Efficiency, yes by grammar+fascist · · Score: 4, Funny

    AMD Says Power Efficiency Still Key

    I'll be happy with these new processors as long as I can still efficiently heat my apartment with them.

    --
    I got my Linux laptop at System76.
    1. Re:Efficiency, yes by Anonymous Coward · · Score: 3, Interesting

      I'm afraid that I'm being a thermodynamics fascist, but you really can't efficiently heat your apartment with CPUs. Typically, for every BTU of heat delivered to you by electrical power, 2 more BTUs go up the power station smokestack or are lost in transmission. In contrast, for every BTU delivered from a modern gas furnace, less than 0.1 BTU goes up the chimney.

    2. Re:Efficiency, yes by Sabre0591 · · Score: 2, Funny

      You've got that right. I heat my spare room with a pair of 64bit AMDs running in two desktop units. Now if I can just figure out where to put the other four maybe I can shut down the furnace this winter.

      --
      The manual said "install Windows XP or better", So I went with Linux.
  11. you don't want to do that... by YesIAmAScript · · Score: 2, Insightful

    I didn't know AMD could do that, as I run Windows and under Windows the two cores speed up and slow down (several steps from 1GHz to 2.2GHz) at the same time.

    But you don't want to do it anyway. If you look at the voltages to the cores, as the cores slow down, the voltage goes down too. This reduces power used and also reduces leakage (which is large at 90nm and can be large at 65nm). The problem is that both cores receive the same voltage, so you can't reduce the voltage to the one core that is slowing down unless the other one slows down too.

    So you'd rather run two cores at 1.7GHz and 1.2V instead of one core at 2.4GHz and 1.4V and one core at 1GHz and 1.4V. The power usage goes down with the square of the voltage, so the former case is saving 25% more power than the latter.

    --
    http://lkml.org/lkml/2005/8/20/95
    1. Re:you don't want to do that... by undeaf · · Score: 2, Interesting

      Okay then. So that means that you can't just shift most of the power to one CPU to make it much more efficient at single threaded tasks, but also that it still should be quite beneficial to run multiple cores at different speeds.

      Assuming that each core is like an individual CPU, odds are, one core is better than the other. That would mean that for both cores to run at the same speed, the better one would have to be getting more voltage than it requires, or be running slower than it could be(those two things are basically equivalent). So the optimal solution would be to link the state of the cores, but for each state, set each CPU to the maximum it can go at that particular voltage.

  12. Power isn't the only criterion by BlueBiker · · Score: 3, Insightful
    So you'd rather run two cores at 1.7GHz and 1.2V instead of one core at 2.4GHz and 1.4V and one core at 1GHz and 1.4V.
    If you have a single thread going flat out, you'll be sacrificing performance if you throttle its core down to achieve voltage parity with a second mostly idle core. Instead of having idle cores drag the speeds down, maybe active cores should push the speeds up.
    1. Re:Power isn't the only criterion by Wesley+Felter · · Score: 2, Interesting

      Instead of having idle cores drag the speeds down, maybe active cores should push the speeds up.

      Exactly. Intel calls this EPI throttling in one of their recent papers.

  13. Re:AMD Says Power Efficiency Still Key by Phil+John · · Score: 2, Informative

    Customers are wanting better power efficiency. Due to the rising costs of energy a lot of data centres are now charging based on energy consumption and heat output (needs more AC -> needs more energy). It's becoming a real problem, especially for some data centres who for varying reasons cannot increase their electricity supplies. That's why google, microsoft and others have started building data centres near a hydro-electric dam in the states, cheap and plentiful electricity.

    --
    I am NaN
  14. X2-3800+ (ADD) has performance/Watt crown by edxwelch · · Score: 2, Informative

    Actually the new low power X2-3800+ (ADD) now has the performance/Watt crown.
    It has idle power of 8 watts and full load of 25 watts.
    They measured the performance of various benchmarks and also the energy required to perform the benchmark to get a figure for performance/Watt and the
    X2-3800+ came out miles ahead of the Conroe (or any other chip). http://www.lostcircuits.com/cpu/low_e/6.shtml