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The Power Supply Matters!

Efficiency: Core 2 Nukes Atom On The Desktop

System efficiency does not only depend on the core components you use, but it is highly dependent on the power supply, since all power supplies have a certain efficiency when they convert 110 or 220/230 V AC power into 3.3 V, 5 V, and 12 V DC power. Depending on how complex the power supply is, and on how it is laid out (one rail, multiple rails), it will demonstrate certain efficiency characteristics.

As all PSUs have a power loss, efficiency is typically rated in percentage terms. The industry standard for measuring and rating efficiency is called 80 Plus, and it splits power supply units into three categories: bronze, silver, and gold. An 80 Plus rating approaches 90% power efficiency at varying loads, taking low, medium, and high loads into account and specifying this as a percentage of the total output.

Here’s the issue: if a 1,000 W power supply unit is rated excellent at low load, this means that “low load” is still a rather high power in the case of our two systems, which idle at less than 30 W. At such a low load, the excellent 80 Plus, 1,000 W power supply unit will show rather pathetic power efficiency just because it wasn’t designed for such a load.

We decided to run the Foxconn G31 system and the Core 2 Duo E7200 with four different power supplies that are rated at 1,000 W, 850 W, 300 W, and 220 W. You will find the results on the following page, and they should convince you to get a power supply that matches your system’s requirements, as the power requirement differences are larger than the difference in power consumption that you would get by exchanging the E7200 for a Core 2 Duo E8600.

1000 W: OCZ EliteXstream 1000

We used a high-end OCZ power supply to test power consumption for such a hardcore power supply unit. The EliteXstream 1000 is an excellent device. Designed by PC Power and Cooling, it is rated 80 Plus and offers an 82% level of efficiency. An active power factor corrector (PFC) and lots of connectors are mandatory for such a high-end product, which is targeted at workstations and high-end gaming. The device comes with an impressive five-year warranty. However, the device is overkill for our low-power systems, as you will see on the next page.

850 W: Coolermaster Real Power Pro RS850 EMBA

Cooler Master’s 850-W RS850-EMBA has been our reference power supply for almost a year. We use it for many of our reviews, as we appreciate its powerful and reliable qualities. It is also backed by a five-year warranty, is 80 Plus compliant, and definitely well-equipped for an enthusiast user’s requirements.

300 W: Etasis EFN-300

We didn’t have a power supply at 400-500 W available at the time we finished this article, but we found a 300 W model by Etasis, the EFN-300. Etasis Electronics is not one of the big, popular brands, and the EFN-300 isn’t special in any way except that it is a no-noise device rated at 300 W output. While it likely will not impress enthusiasts, the power supply unit helped to decrease the system’s power consumption compared to the Cooler Master and OCZ power units.

220 W: Fortron FSP220

If you remember our recent articles on VIA’s Nano vs. the Intel Atom and the comparison of Foxconn and Gigabyte G31 motherboards, then you might also remember the FSP220 from Fortron, which is a compact 220 W power supply.

This one is rated for an even lower maximum output and some of you might wonder why we even bothered to use it. Clearly, this is the power supply that allowed us to reach the lowest overall power consumption numbers, as it is capable of answering the power demands of the Atom and Core 2 systems at a much higher efficiency level than the other power supply units we tried.

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  • 8 Hide
    slomo4sho , November 21, 2008 8:44 AM
    Thanks for the write up. I wish you actually compared the Atom to cheaper AMD CPUs like the 4850e instead of the core 2 though.
  • 0 Hide
    zodiacfml , November 21, 2008 9:02 AM
    quick follow up from the article on Efficient Motherboards which i mentioned that the power supply matters more than the motherboard for power efficiency.
    what's good in low power supplies is not really the efficiency, but they're lower in price and is usually less noisy. so indeed,you're right about to match the powersupply to the usual activity of the computer.

    the existence of an atom is not about power efficiency but lower die space then lower costs. as you see, the core2duo is almost 4 times the die space of the atom which reflects the three times performance advantage. also, i predict the atom will be more efficient at 0.8-1 GHz since the 1.6Ghz default speed is pretty high for this small chip.

    so, an atom system it is for NAS/server requirements. :) 
  • -1 Hide
    chouff , November 21, 2008 9:17 AM
    Slomo4shOThanks for the write up. I wish you actually compared the Atom to cheaper AMD CPUs like the 4850e instead of the core 2 though.

    They kind of did, here:,2038-5.html
  • 2 Hide
    blackwidow_rsa , November 21, 2008 9:23 AM
    The article states that the e7200 has a 800mhz fsb? shouldnt it be 1066mhz?
  • 3 Hide
    slomo4sho , November 21, 2008 9:27 AM
    chouffThey kind of did, here: [...] 038-5.html

    Thats hardly a equal comparison... The AMD system was in no way build for power efficiency as it had a 4670 GPU.

    I want to see a fair representation of how well AMD holds up in the Power vs Performance discussion. Considering that you can get a MOBO + a 4850e for the price of a E7200, I would like to see how the two would compare when it comes to efficiency. Its also pretty unfair assessment of the atom vs a dual core processor, they really should have obtained a 330 for a more accurate assessment.

    Also, when will we be seeing a write-up on a variety of >400watt PSUs?
  • 4 Hide
    Mucke , November 21, 2008 10:35 AM
    Absolutely. If I want an efficient system I will take a 4850e + 780G-Board. It will still need more power but it will be usable in every day life without limitations.
  • 4 Hide
    Shadow703793 , November 21, 2008 11:19 AM
    What Intel needs to do is create a new chipset specifically for Atom. The Chipset uses up most of the power.
  • 1 Hide
    zenmaster , November 21, 2008 11:27 AM
    Intel's Chipsets overall need a examination from a power point of view.
    I think they are still on the 65nm process?
  • -1 Hide
    Pei-chen , November 21, 2008 11:39 AM
    Great article; I always knew nettop is a fad. It is too bad that sub 350w PSU is very difficult to find.
  • 4 Hide
    nihility , November 21, 2008 11:50 AM
    I don't understand why you didn't underclock/undervolt the C2D processor (and atom too). That would have been very meaningful data.
  • 1 Hide
    kureshii , November 21, 2008 12:24 PM
    The results are not all that surprising; in terms of power efficiency, the Atom setup is already "crippled" by the 945GC. It would be nice to do a rerun once Poulsbo mini-ITX motherboards are out. There are already some available, but they are not quite mainstream yet.

    I'm pretty sure the Core 2 will still beat out Atom+Poulsbo for more processor-intensive applications, but I'd like to see how the significantly lower idle power for Poulsbo will affect things.
  • 1 Hide
    pullmyfoot , November 21, 2008 1:29 PM
    An ok writeup. Pretty interesting. However it seems like the article was just thrown together without much thought of the content - the scope is so extremely limited. 2 CPUs? common.. You can do better than that. This seems to be the case with most of their recent articles and it seems like these articles are just there for the sake of being there.

    What happened to AMD CPUs? And it would be interesting to see how the E7200 performed undervolted and underclocked. Seeing how close its idle power is to the Atom, it might even take up less power.
  • 1 Hide
    enewmen , November 21, 2008 1:48 PM
    Just wondering.
    I have a 4 year old Pentium M @ 1400 Mhz.
    Seems plenty fast enough - can even play Oblivion on low settings. This makes me wonder if the Atom is fully capable of everyting except for media recoding, high-end games, etc.
    The Pentium M would have been a better comparison since everyone knows the C2D is whole lot faster, etc. blah blah
  • -1 Hide
    zcubed , November 21, 2008 2:33 PM
    great article. i wonder what the e7200 would perform like in a mini-itx board power-wise. there are 6 available(3 different types of chipsets) on newegg that will support it. that would probably also be a more even comparison with the atom.
  • 0 Hide
    Anonymous , November 21, 2008 2:39 PM

    i really wish for this kind of comparison, you include the intel Pentium-M & Pentium-III M for comparison.

    I have an intel Pentium-M, and I wish I know if I upgrade to intel atom would it be faster or slower.
  • 0 Hide
    JimmiG , November 21, 2008 2:49 PM
    Pretty interesting, but the point of the Atom isn't to give the most performance per watt. It's about providing "good enough" performance for stuff like browsing the Internet, at the targeted power draw. If you plan on doing rendering, gaming, converting video etc., a low-end Core 2 is a better choice. Also current Atom chipsets draw much more than the CPU itself which kind of defeats the purpose of the Atom on the desktop (mini-ITX). This will improve once Atom gets its own memory controller, possibly integrated GPU core, and Intel comes out with more efficient chipsets. Finally the cheapest Atom CPU costs $29, quite a bit cheaper than any Core 2 CPU.
  • 0 Hide
    nmathew , November 21, 2008 2:54 PM
    nihilityI don't understand why you didn't underclock/undervolt the C2D processor (and atom too). That would have been very meaningful data.

    I fully agree. In my experience, C2D processors easily undervolt a fair bit. Set the C2D to a 800MHz bus, and look out. I wonder how close the e7200 or the lower L2 cache E5200 underclocked and undervolted could get to passive cooling. Furthermore, while I understand the desire for an apples to apples comparison, testing the e7200 with a lower power modern chipset would have been nice. There is no real need to hamper it with an older inefficient platform if the goal is to show that a C2D system can be more efficient in low wattage situations than an Atom based one.
  • 0 Hide
    Christos , November 21, 2008 3:16 PM
    The point of Atom isn't just low power requirements. It's about small die size in order to be used for netbooks. Try to fit a celeron in one...

    I believe the desktop versions of Atom aren't really useful. As this article proves using a low end ordinary desktop cpu can do more for the same power draw.

    Since i have a quite powerful desktop pc, but i need some portability too, i chose an Acer Aspire One. I really love it! It can do much more than browsing the net. I use it for developing in Visual Studio 2008, i use Office 2007, i even play games like Star Wars KOTOR with it. Atom may not be similar in performance to Core 2, but it is perfect for netbooks and provides more than enough power for the average user.

    But frankly there is no point in bying an Atom for a desktop pc.
  • 0 Hide
    Area51 , November 21, 2008 3:21 PM
    Shadow703793What Intel needs to do is create a new chipset specifically for Atom. The Chipset uses up most of the power.

    I think they are including an IMC on the next version.. That should reduce power consumption to the platform significantly.
  • -2 Hide
    tsponholz , November 21, 2008 3:26 PM
    Love the comparison...

    I have some follow up questions that the board may be able to answer:
    1) Since system power maxed at
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