Measuring Bandwidth

Stream measures "sustainable memory bandwidth" and is thus a good indication of how a CPU will handle data intensive applications. Dr. John McCalpin is the developer and maintainer of the STREAM benchmark.

We compiled with gcc 4.7 on all platforms and used the -O3 -fopen -static settings. It is important to remark that this version of gcc has been optimized by the Linaro group, a non-profit software engineering effort. Linaro's objective is to optimize the kernel and typical tools for the ARM-Cortex A-series CPUs.

On the Intel CPUs we force the threads to make use of Hyper-Threading with taskset. So for example, the four threads measurement is done on two physical cores with four threads. This gives an idea of how a quad-core ARM server node compares to a virtual machine that gets a few physical and few logical cores from the hypervisor. It also allows us to evaluate how two threads on top of an Atom core compare to two ARM cores. When you compare CPUs with similar power consumption, you typically get two ARM cores for each Hyper-Threaded Atom core.

Stream Triad—1 to 4 threads

The ARM based server is a pretty bad choice right now for memory intensive workloads. Even with four cores and DDR3-1333, the useable bandwidth is less than one sixth of what one Xeon core can sustain.

In a similar vein, the ECX-1000 is not capable of providing more bandwidth than an Atom system equipped with DDR2-667. However, both the Atom and ARM cores are pretty bad when it comes to bandwidth. Although the specs claim that the CPUs can drive one channel of DDR3-1066, the measured bandwidth comes nowhere near the theoretical 8.5GB/s that such a DIMM can deliver.

Benchmarking Configuration Integer Processing
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  • thenewguy617 - Wednesday, March 13, 2013 - link

    I would like to see the results with the website running on bare metal. I would like to, but I don't believe you when you say the virtualization overhead is minimal.
    Also, did you include the power used by the switch? as we scale the xeon cluster we will add a lot of cost and power in the network, however Calxeda fabric should scale for free.
  • thebeastie - Thursday, March 14, 2013 - link

    I think a lot of you are missing the main point or future potential of this server technology. And that is that intel like to make an absolute minimum of $50 per CPU they make, in server CPUs it's more like $300.

    These Arm CPUs are being sold at around $10 a CPU.
    Sure Caldexa have gone the hard yards making such a server and want a lot of money for it. BUT once these ARM servers are priced in relative context of their actual CPu costs its going to be the biggest bomb drop on Intels sever profits in history.
  • Silma - Thursday, March 14, 2013 - link

    Assuming you are right and ARM is becoming so important that it can't be ignored, what's to prevent Intel to produce and sell ARM itself? In fact what's to prevent Intel to produce the best ARM socs as it has arguably the best fabs?
    There are rumors that Apple is asking Intel to produce procs for them, this would certainly be very interesting if it proves to be true.
  • thebeastie - Friday, March 15, 2013 - link

    The fact that Intel would practically look at other businesses then produce SoC/CPUs for $10 each, x86 or ARM based doesn't matter in the face of such high portability of code.
  • Metaluna - Friday, March 15, 2013 - link

    The problem is that ARM cores are pretty much a commodity, so ARM SoC pricing is inevitably going to end up as a race to the bottom. This could make it difficult for Intel to sustain the kind of margins it needs to keep it's superior process R&D efforts going. Or at least, it would need to use its high-margin parts to subsidize R&D for the commodity stuff which could get tricky given the overall slowing of the market for the higher end processors. I think this is what's happening with the supposed Apple deal. There have been reports that they have excess capacity at 22nm right now so it makes sense to use it. And, since Apple only sells its processors as part of its phones and tablets, it doesn't directly compete with x86 on the open market.

    Of course, all the other fabs are operating under the same cost constraints, so there would be an overall slower pace of process improvements (which is happening anyway as we get closer to the absolute limits at <10nm).
  • wsw1982 - Wednesday, April 3, 2013 - link

    And so does those companies, run into bottom. What can they do to even their R&D, by put the server chip into mobile phone?
  • Krysto - Monday, March 18, 2013 - link

    Yup. This is actually Intel's biggest threat by far. It's not the technical competition (even though Intel's Atom servers don't seem nearly as competitive as these upcoming ARM servers), but the biggest problem by far for them will be that they will have to compete with the dozen or so ARM server companies on price, while having more or less the same performance.

    THAT is what will kill Intel in the long term. Intel is not a company built to last on Atom-like profits (which will get even lower once the ARM servers flood the market). And they can forget about their juicy Core profits in a couple of years.
  • wsw1982 - Wednesday, April 3, 2013 - link

    So your argument is because the ARM solution is more expensive than Intel solution now, therefore it must be cheaper than Intel solution in the feature? The mobile ARM is cheap, so does the Intel mobile chips.
  • Silma - Thursday, March 14, 2013 - link

    1300$ difference / server, that's a lot electricity you have to spare to justify the cost, especially as it is better that Xeon servers only in a few chosen benchmarks.

    Can't see how this is interesting in production environment.
    It's more for testing / experimenting I guess;
  • Wilco1 - Thursday, March 14, 2013 - link

    The savings are more than just electricity cost, you also save on cooling costs and can pack your server room more densely. If you do a TCO calculation over several years it might well turn out to be cheaper overall.

    This is the first ARM server solution, so it's partly to get the software working and test the market. However I was surprised how competitive it is already, especially when you realize they use a relatively slow 40nm Cortex-A9. The 2nd generation using 28nm A15 will be out in about 6 months, if they manage to double performance per core at similar cost and power then it will look even better.

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