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The ARM vs x86 Wars Have Begun: Power Analysis of Atom, Krait, and Cortex A15

80 points by lispython 14y ago

kevingadd 14y ago
The graphs in this article border on unreadable. I don't know why you'd post graphs like that unsmoothed unless your goal was for your readers to ignore them completely. The claims he makes about power consumption certainly seem interesting, but I don't really feel like I can take them without a grain of salt given how hard it is to read a lot of the graphs he's drawing conclusions from. The general trend of Atom finishing benchmarks earlier without drawing much more power is pretty interesting, at least. I never would have guessed that Atom would be a winner here - it has such a bad reputation.
- mtgx 14y ago
  The bad reputation came from the low performance (in low-end Windows machines), and it looks like it will continue to have that now that Cortex A15 is out. From the power consumption point of view, it was completely unusable for a smartphone or tablet until recently, because when they made it, Atom had a 10W TDP, and for the past 5 years they've mainly tried to get that to 2W, while keeping the performance mostly unchanged. That performance used to be much higher than the high-end ARM chip at the time when they released it, but that's not the case anymore.
  - dspillett 14y ago
    Another key problem with early Atom based machines was the rest of the chipset (io controller and such) that went with them, which could draw a fair amount of power too. I presume this has been improved as well as the CPU's power needs.
sami36 14y ago
There is no war to be had until Intel seriously considers operating on much lower margins. Their problem is not just idle power & heat dissipation, their real problem is cost/ unit. Whatever Intel does going forward, their fat days are over.
- ricw 14y ago
  Indeed. Their business model needs changing. It's not just price, it's also the fact that they don't offer as many flavours of SoC, aka with different basebands or integrated encoders, to even compete closely with the ARM ecosystem. Technically they may now be able to compete, from a business perspective: not!
- EwanToo 14y ago
  Exactly, I think you're 100% right. The real "war" is a price one. If Intel are willing to cannibalise their own per-CPU margins, they'll sell bucket loads of mobile chips. If they're not, then they won't - it's not much harder than that to understand. I can see why they wouldn't be willing, once you get a relatively high performance Atom chip then the use case for a highly profitable Xeon chip becomes much narrower.
- yk 14y ago
  Intel is producing Atoms on an ancient process, while they are one generation ahead of every body else in cutting edge process. So this is Intel getting its feet wet, not Intel trying to compete. And atop of this, I am pretty sure there is a market for really high powered smart phones above the current price range. [Edit: reformulated last sentence]
  - WatchDog 14y ago
    I'm curious as to what will be the applications that drive the need for more phone performance. I am pretty happy with the performance of my S3, if it were four times faster, I don't see how it is going to noticeably improve my user experience.
    - yk 14y ago
      Actual desktop replacement. Think about a phone with similar specs as a three year old desktop. You can then carry your desktop around, do actual work wherever you find a reasonable screen and keyboard and you do no longer need to sync several devices. Apart from this, any real augmented reality application can easily burn any excess computing power you may carry.
dman 14y ago
Anand does an exceptional job of acting as a proxy for Intel's marketing department.
- sixbrx 14y ago
  This comment would have a lot more force with specifics that show how Anand/Intel's numbers are wrong or misleading.
  - polshaw 14y ago
    I think the parent post is too strong, but numbers are by no means the only way of showing a bias. Whilst i believe he tries to be objective, Anand may hold a slight bias towards intel. Take the discussion of the future; he talks of the advancements of the core architecture, comparing a yet-unseen 8W TDP[1] haswell, then talking confidently of halving that at 14nm. This is in no means a certainty; i think it is fair to say this would be a best-case scenario where intel focused fully on reducing power, as well as having a very successful 14nm node. On top of this, there is no mention of price in this equation; i can't see a 'core' CPU in a nexus tablet (too expensive for the cost) or an ipad (too expensive for apple's margins) if intel want to keep their margins. I should reiterate that everyone has a bias, and if Anand's is slightly pro-intel, then it is surely propagated by the high level of access intel seem to give him (take for example the 'x86 power myth busted' article; where the atom was compared to the intel cherry-picked (outdated) tegra3), and the fact that we have a very capable intel today. As said i believe he attempts to be objective still, so i still think his journalism is some of if not the best in this area. 1. keep in mind TDP is not peak power (which is where the A15 would be close to 4W), but the sustained heat output that should be dissipated in whatever enclosure, for which there is no standard. This would put the A15 in the 1-2W range.
    - sixbrx 14y ago
      That's the kind of specifics I was looking for (thanks). I agree about numbers, and one doesnt have to answer with numbers if they can be brushed aside with specifics that offer proper perspective. I'm pretty hardware-ignorant myself, so I'd be at the mercy of articles like this if it weren't for comments. It's interesting times - the stakes seem to be high because of the way that some platforms are tied to hardware architectures (which is my real interest here).
macavity23 14y ago
A question for iOS devs out there: how tied to ARM is iOS Objective-C programming? I ask because Android already supports Atom-based devices, and presumably Win8RT apps are easy to recompile for Intel - so it seems likely that it would be straightforward for any of the players in the mobile space to switch architectures on fairly short notice.
- melling 14y ago
  Objective-C was created in 1983. http://en.wikipedia.org/wiki/Objective-C http://en.wikipedia.org/wiki/Objective-C Apple and NeXTStep have run on Intel, Motorola 68k, or PowerPC chips in the past. iOS is a subset of Mac OS, which currently runs on Intel. In short, the CPU architecture choice is irrelevant.
  - deleted 14y ago
    [deleted]
  - wtallis 14y ago
    You left out SPARC and PA-RISC. NeXTSTEP was probably the most cross-platform desktop OS ever sold.
- ConstantineXVI 14y ago
  As mentioned, Apple has plenty of experience switching architectures, so technically it's not a huge issue. Don't hold your breath though; since Apple's going out of it's way to build custom ARM cores now, it's safe to assume ARM (or if anything, a custom arch sooner than Intel) is their future now. Apple got burned when IBM couldn't keep up power/performance on PowerPC, leaving their fate entirely to a third-party is a mistake they're unlikely to make again.
- yk 14y ago
  Not an iOS dev, so I can not tell you how much inline assembler magic is in apps. But the operating system needs of course a fair amount of plattform specific code, as does the compiler. And in general quite a few optimizations are platform specific. So even though Apple uses llvm, the swap is a lot more involved than a -march=x64 compiler flag. This is also true for Android and WinRT.
trotsky 14y ago
You'll notice that Intel isn't coming to Anandtech and offering to break open a bunch of android phones and comparing them with the atom android port. On windows Intel is benefitting from a kernel and compiler that's spent 15 years being optimized for their isa. I am sure qualcomm worked very hard with microsoft getting RT out the door but I would wager that there is a lot more room left for optimization of krait on windows rt than there is for atom on windows 8. Intel and Acer also have a lot of experience optimizing for the hard separation between the platform code and the os which typically involves a lot of cheating / second guessing. I'm pretty sure microsoft requires their arm platforms to support the traditional x86 style platform interfaces like uefi and acpi. Arm SOC manufacturers gave traditionally benefitted from being able to do deep integration into the OS and exploit tons of manufacturer specific optimizations. I highly doubt qualcomm enjoyed the same freedom with the NT kernel. So while it's impressive to see atom operating with much better gating than it traditionally has had, I suspect that if you did the comparison on neutral ground using gcc on linux and let all the manufacturers do as much optimizing as they wanted you'd see the arm systems improving their performance per watt significantly. Meanwhile the atom would be lucky to just tread water.
- WatchDog 14y ago
  You can argue it both ways, one the one hand windows benefits from the last 15 years of x86 optimization. On the other hand arm is benefiting from a lifetime of embedded optimization. Intel has only relatively recently shifted their focus to low wattage parts, and this demonstration on atom is not on their latest process. What this benchmark shows is that the speculation about x86 being inherently inferior to ARM for low wattage is just that, speculation. x86 and Arm are very much in the same ballpark and we can expect the competition to really heat up in the coming years.
  - deleted 14y ago
    [deleted]
vondur 14y ago
I believe that one overlooked fact is the ability of a company to purchase a license to design an ARM processors for their own particular usage scenarios as Apple has done. I believe this gives ARM a distinct advantage vs. Intel. With Intel you have to wait until they release a processor and then you have to integrate into your design. I think the ARM way of doing licensing will be a boon for them.
yk 14y ago
I think Intel is in an interesting business position. Just when AMD is getting into serious trouble, raising possible anti trust issues, ARM steps up. However ARM has actually the inferior architecture (for desktop/ modern tablet use).[1] So they can avoid anti trust issues by pointing to a competitor, who simply does not threaten Intels core revenue generators ( Desktops, Notebook [2]). [1] I belive they still use in order architecture. And certainly no one but Intel has a 22nm fin fet process running. [2] I am actually not as sure about servers.
- wolf550e 14y ago
  A15 is out of order.
  - yk 14y ago
    Thanks, I should have checked that. ( The argument is probably about prefetch logic, but basically similar.)
    - mtgx 14y ago
      Cortex A9 was out of order, too. Ironically, Atom is still in-order.
ChuckMcM 14y ago
This is a fascinating article both in what it says, and what it doesn't say. If the future is really low powered SoC's then Intel is in a world of hurt. The reason for that is that if Intel can only match power/performance of ARM in their chips, then its a toss up for the manufacturer in terms of user visible impact on which to use, and that makes cost and/or differentiation the next selector in the 'whose do we buy' tree. If Intel has to go to the mat on price it really kills their business model. One of the amazing things about Intel over the last 20 years has been that their part sells for up to 30% of the total cost of all parts of the system. And what that means is that if you get the CPU for half as much you save 15% on your total parts cost. That is huge savings. But if Intel has to cut their margins to get sales, they lose a lot of R&D dollars and their legendary advantage in Fabrication is suddenly underfunded. That is a huge problem for them. Intel has to win this fight or they will have to radically change the way they have structured their business. The second part is differentiation. Intel just doesn't license the x86 architecture any more, they got out of that when competitors were out executing them in architecture design. What that means is that you really can't add an instruction if you're an Apple or a Cisco or what not to your CPU to make your particular use of the part more efficient. But with ARM you can. If you are an instruction set licensee you can make internal changes and keep the compatibility high. Apple just demonstrated with the A5x that this was something they were willing to do. There is no relationship with Intel where that sort of option would be possible. So if Intel can only match ARM on its performance and power curves, they lose. They have to be either 50% faster at the same power levels on the same workload, or 50% more efficient at the same performance. +/- 10% or so isn't going to cut it when they are commanding a huge chunk of the parts cost.
- twoodfin 14y ago
  Apple just demonstrated with the A5x that this was something they were willing to do. Is that right? I thought the two license types were for the full core designs (for those who just want to stamp out a pre-designed core) and an ISA license (for those who want to craft their own implementation). I was unaware having an ISA license entitled Apple to introduce new instructions, nor that they had added new instructions to the A6. (The A5x, AFAIK, is just a Cortex A9 at heart).
green7ea 14y ago
Has anyone else noticed how odd these benchmarks seem? They run sunspider on different browsers in different OSes and use the results to compare processor performance per watt. On the same OS, with the same browser, I can have higher variations on performance per watt with a single compiler flag (fastmath, -O2 vs -O3, etc). The same could be said by changing the kernel's scheduler. If we keep in mind that the browser, compiler and OS are all different for these tests, how can we accept the results as anything but noise from those differences? One striking example of this is that the new version of chrome on the nexus 10 could easily account for the performance difference in the kraken test. How can we use that data to compare the performance per watt of the processors?
InclinedPlane 14y ago
Let's remember that Intel is sitting on a mountain of cash and even more importantly mountains of chip design talent and mountains of fab hardware. Intel can afford to play the long game. The interesting thing is how competitive Intel's first gen x86 part has been.

80 points by lispython 14y ago

The graphs in this article border on unreadable. I don't know why you'd post graphs like that unsmoothed unless your goal was for your readers to ignore them completely. The claims he makes about power consumption certainly seem interesting, but I don't really feel like I can take them without a grain of salt given how hard it is to read a lot of the graphs he's drawing conclusions from. The general trend of Atom finishing benchmarks earlier without drawing much more power is pretty interesting, at least. I never would have guessed that Atom would be a winner here - it has such a bad reputation.

mtgx 14y ago
The bad reputation came from the low performance (in low-end Windows machines), and it looks like it will continue to have that now that Cortex A15 is out. From the power consumption point of view, it was completely unusable for a smartphone or tablet until recently, because when they made it, Atom had a 10W TDP, and for the past 5 years they've mainly tried to get that to 2W, while keeping the performance mostly unchanged. That performance used to be much higher than the high-end ARM chip at the time when they released it, but that's not the case anymore.
- dspillett 14y ago
  Another key problem with early Atom based machines was the rest of the chipset (io controller and such) that went with them, which could draw a fair amount of power too. I presume this has been improved as well as the CPU's power needs.

sami36 14y ago

There is no war to be had until Intel seriously considers operating on much lower margins. Their problem is not just idle power & heat dissipation, their real problem is cost/ unit. Whatever Intel does going forward, their fat days are over.

ricw 14y ago
Indeed. Their business model needs changing. It's not just price, it's also the fact that they don't offer as many flavours of SoC, aka with different basebands or integrated encoders, to even compete closely with the ARM ecosystem. Technically they may now be able to compete, from a business perspective: not!
EwanToo 14y ago
Exactly, I think you're 100% right. The real "war" is a price one. If Intel are willing to cannibalise their own per-CPU margins, they'll sell bucket loads of mobile chips. If they're not, then they won't - it's not much harder than that to understand. I can see why they wouldn't be willing, once you get a relatively high performance Atom chip then the use case for a highly profitable Xeon chip becomes much narrower.
yk 14y ago
Intel is producing Atoms on an ancient process, while they are one generation ahead of every body else in cutting edge process. So this is Intel getting its feet wet, not Intel trying to compete. And atop of this, I am pretty sure there is a market for really high powered smart phones above the current price range. [Edit: reformulated last sentence]
- WatchDog 14y ago
  I'm curious as to what will be the applications that drive the need for more phone performance. I am pretty happy with the performance of my S3, if it were four times faster, I don't see how it is going to noticeably improve my user experience.
  - yk 14y ago
    Actual desktop replacement. Think about a phone with similar specs as a three year old desktop. You can then carry your desktop around, do actual work wherever you find a reasonable screen and keyboard and you do no longer need to sync several devices. Apart from this, any real augmented reality application can easily burn any excess computing power you may carry.

dman 14y ago

Anand does an exceptional job of acting as a proxy for Intel's marketing department.

sixbrx 14y ago
This comment would have a lot more force with specifics that show how Anand/Intel's numbers are wrong or misleading.
- polshaw 14y ago
  I think the parent post is too strong, but numbers are by no means the only way of showing a bias. Whilst i believe he tries to be objective, Anand may hold a slight bias towards intel. Take the discussion of the future; he talks of the advancements of the core architecture, comparing a yet-unseen 8W TDP[1] haswell, then talking confidently of halving that at 14nm. This is in no means a certainty; i think it is fair to say this would be a best-case scenario where intel focused fully on reducing power, as well as having a very successful 14nm node. On top of this, there is no mention of price in this equation; i can't see a 'core' CPU in a nexus tablet (too expensive for the cost) or an ipad (too expensive for apple's margins) if intel want to keep their margins. I should reiterate that everyone has a bias, and if Anand's is slightly pro-intel, then it is surely propagated by the high level of access intel seem to give him (take for example the 'x86 power myth busted' article; where the atom was compared to the intel cherry-picked (outdated) tegra3), and the fact that we have a very capable intel today. As said i believe he attempts to be objective still, so i still think his journalism is some of if not the best in this area. 1. keep in mind TDP is not peak power (which is where the A15 would be close to 4W), but the sustained heat output that should be dissipated in whatever enclosure, for which there is no standard. This would put the A15 in the 1-2W range.
  - sixbrx 14y ago
    That's the kind of specifics I was looking for (thanks). I agree about numbers, and one doesnt have to answer with numbers if they can be brushed aside with specifics that offer proper perspective. I'm pretty hardware-ignorant myself, so I'd be at the mercy of articles like this if it weren't for comments. It's interesting times - the stakes seem to be high because of the way that some platforms are tied to hardware architectures (which is my real interest here).

macavity23 14y ago

A question for iOS devs out there: how tied to ARM is iOS Objective-C programming? I ask because Android already supports Atom-based devices, and presumably Win8RT apps are easy to recompile for Intel - so it seems likely that it would be straightforward for any of the players in the mobile space to switch architectures on fairly short notice.

melling 14y ago
Objective-C was created in 1983. http://en.wikipedia.org/wiki/Objective-C http://en.wikipedia.org/wiki/Objective-C Apple and NeXTStep have run on Intel, Motorola 68k, or PowerPC chips in the past. iOS is a subset of Mac OS, which currently runs on Intel. In short, the CPU architecture choice is irrelevant.
- deleted 14y ago
  [deleted]
- wtallis 14y ago
  You left out SPARC and PA-RISC. NeXTSTEP was probably the most cross-platform desktop OS ever sold.
ConstantineXVI 14y ago
As mentioned, Apple has plenty of experience switching architectures, so technically it's not a huge issue. Don't hold your breath though; since Apple's going out of it's way to build custom ARM cores now, it's safe to assume ARM (or if anything, a custom arch sooner than Intel) is their future now. Apple got burned when IBM couldn't keep up power/performance on PowerPC, leaving their fate entirely to a third-party is a mistake they're unlikely to make again.
yk 14y ago
Not an iOS dev, so I can not tell you how much inline assembler magic is in apps. But the operating system needs of course a fair amount of plattform specific code, as does the compiler. And in general quite a few optimizations are platform specific. So even though Apple uses llvm, the swap is a lot more involved than a -march=x64 compiler flag. This is also true for Android and WinRT.

trotsky 14y ago

You'll notice that Intel isn't coming to Anandtech and offering to break open a bunch of android phones and comparing them with the atom android port. On windows Intel is benefitting from a kernel and compiler that's spent 15 years being optimized for their isa. I am sure qualcomm worked very hard with microsoft getting RT out the door but I would wager that there is a lot more room left for optimization of krait on windows rt than there is for atom on windows 8. Intel and Acer also have a lot of experience optimizing for the hard separation between the platform code and the os which typically involves a lot of cheating / second guessing. I'm pretty sure microsoft requires their arm platforms to support the traditional x86 style platform interfaces like uefi and acpi. Arm SOC manufacturers gave traditionally benefitted from being able to do deep integration into the OS and exploit tons of manufacturer specific optimizations. I highly doubt qualcomm enjoyed the same freedom with the NT kernel. So while it's impressive to see atom operating with much better gating than it traditionally has had, I suspect that if you did the comparison on neutral ground using gcc on linux and let all the manufacturers do as much optimizing as they wanted you'd see the arm systems improving their performance per watt significantly. Meanwhile the atom would be lucky to just tread water.

WatchDog 14y ago
You can argue it both ways, one the one hand windows benefits from the last 15 years of x86 optimization. On the other hand arm is benefiting from a lifetime of embedded optimization. Intel has only relatively recently shifted their focus to low wattage parts, and this demonstration on atom is not on their latest process. What this benchmark shows is that the speculation about x86 being inherently inferior to ARM for low wattage is just that, speculation. x86 and Arm are very much in the same ballpark and we can expect the competition to really heat up in the coming years.
- deleted 14y ago
  [deleted]

vondur 14y ago

I believe that one overlooked fact is the ability of a company to purchase a license to design an ARM processors for their own particular usage scenarios as Apple has done. I believe this gives ARM a distinct advantage vs. Intel. With Intel you have to wait until they release a processor and then you have to integrate into your design. I think the ARM way of doing licensing will be a boon for them.

yk 14y ago

I think Intel is in an interesting business position. Just when AMD is getting into serious trouble, raising possible anti trust issues, ARM steps up. However ARM has actually the inferior architecture (for desktop/ modern tablet use).[1] So they can avoid anti trust issues by pointing to a competitor, who simply does not threaten Intels core revenue generators ( Desktops, Notebook [2]). [1] I belive they still use in order architecture. And certainly no one but Intel has a 22nm fin fet process running. [2] I am actually not as sure about servers.

wolf550e 14y ago
A15 is out of order.
- yk 14y ago
  Thanks, I should have checked that. ( The argument is probably about prefetch logic, but basically similar.)
  - mtgx 14y ago
    Cortex A9 was out of order, too. Ironically, Atom is still in-order.

ChuckMcM 14y ago

This is a fascinating article both in what it says, and what it doesn't say. If the future is really low powered SoC's then Intel is in a world of hurt. The reason for that is that if Intel can only match power/performance of ARM in their chips, then its a toss up for the manufacturer in terms of user visible impact on which to use, and that makes cost and/or differentiation the next selector in the 'whose do we buy' tree. If Intel has to go to the mat on price it really kills their business model. One of the amazing things about Intel over the last 20 years has been that their part sells for up to 30% of the total cost of all parts of the system. And what that means is that if you get the CPU for half as much you save 15% on your total parts cost. That is huge savings. But if Intel has to cut their margins to get sales, they lose a lot of R&D dollars and their legendary advantage in Fabrication is suddenly underfunded. That is a huge problem for them. Intel has to win this fight or they will have to radically change the way they have structured their business. The second part is differentiation. Intel just doesn't license the x86 architecture any more, they got out of that when competitors were out executing them in architecture design. What that means is that you really can't add an instruction if you're an Apple or a Cisco or what not to your CPU to make your particular use of the part more efficient. But with ARM you can. If you are an instruction set licensee you can make internal changes and keep the compatibility high. Apple just demonstrated with the A5x that this was something they were willing to do. There is no relationship with Intel where that sort of option would be possible. So if Intel can only match ARM on its performance and power curves, they lose. They have to be either 50% faster at the same power levels on the same workload, or 50% more efficient at the same performance. +/- 10% or so isn't going to cut it when they are commanding a huge chunk of the parts cost.

twoodfin 14y ago
Apple just demonstrated with the A5x that this was something they were willing to do. Is that right? I thought the two license types were for the full core designs (for those who just want to stamp out a pre-designed core) and an ISA license (for those who want to craft their own implementation). I was unaware having an ISA license entitled Apple to introduce new instructions, nor that they had added new instructions to the A6. (The A5x, AFAIK, is just a Cortex A9 at heart).

green7ea 14y ago

Has anyone else noticed how odd these benchmarks seem? They run sunspider on different browsers in different OSes and use the results to compare processor performance per watt. On the same OS, with the same browser, I can have higher variations on performance per watt with a single compiler flag (fastmath, -O2 vs -O3, etc). The same could be said by changing the kernel's scheduler. If we keep in mind that the browser, compiler and OS are all different for these tests, how can we accept the results as anything but noise from those differences? One striking example of this is that the new version of chrome on the nexus 10 could easily account for the performance difference in the kraken test. How can we use that data to compare the performance per watt of the processors?

InclinedPlane 14y ago

Let's remember that Intel is sitting on a mountain of cash and even more importantly mountains of chip design talent and mountains of fab hardware. Intel can afford to play the long game. The interesting thing is how competitive Intel's first gen x86 part has been.