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Intel DN2800MT CedarView Atom mini-ITX board power draw testing with Linux and Windows 7
Has single digit power consumption arrived?first published: 13-March-2012 Intel's third generation Atom CPUs (nicknamed CedarView) have had long gestation period since they were originally due last autumn but only started to show up in shops on motherboards in the last few weeks and in many places are still hard to get hold of. The main reason for these delays was allegedly difficulties with the graphics drivers, as Intel chose to use a PowerVR SGX 545 GPU core rather than an in-house GPU core as had been used in all previous Atoms (except the Zxx series). One of the main promises of this new 32nm Atom generation is reduced power consumption, while at the same time providing increased performance. On paper this certainly appears to be achieved as CedarView Atoms sport higher clock speeds with lower TDPs than their previous generation Pineview counterparts (check out our Pineview Atom overview for a comparison). Since the cpu core of the CedarView Atoms is essentially the same as the cpu core of Pineview Atoms (except for the die shrink from 45nm to 32nm) increased cpu performance with higher clocks speeds is practically assured.
In this review we will therefore concentrate on the more interesting promise of reduced power consumption by testing power draw of the Intel DN2800MT mini-ITX motherboard, which features a CedarView dual-core Atom N2800 and a NM10 Southbridge chip (together they are known as the Cedar Trail platform). The Intel DN2800MT is the natural successor of the popular but nowadays obsolete Intel D945GSEJT motherboard which was based on the first generation single core Atom N270.
Other than that the DN2800MT has improved noticeably compared to the D945GSEJT. The DN2800MT features 2 mini-PCIe sockets (one full and one half size), a PCI-e x1 slot (instead of the obsolete PCI slot on the D945GSEJT), two SoDIMM slots for a maximum of 4GB DDR3 RAM (at 1066 MHz), several video output options (VGA, HDMI, LVDS and embedded DisplayPort) and an Intel 82574L Gigabit Ethernet chip (rather than a Realtek one on the D945GSEJT). Sound is provided by a Realtek ALC888S audio chip and one of the SATA ports is multiplexed to the full size mini-PCIe socket to enable the use of mSATA SSDs.
For our tests we are using the following setup:
For the power consumption measurements we use a Profitec KD-302 Watt meter, which has a usable range of 0.2-3600 Watts and was found to be one of the most precise Watt meters even when measuring low power draws, in a Watt meter comparison test done by the well regarded German IT magazine c't (c't 24/2008, pages 226-231). In the following tests we concentrate on idle power draw comparing various Linux distros and Windows 7 Home Premium SP1 (32 bit). We have included tests of a plain installation of Windows 7 SP1 (with all the latest official drivers for the DN2800MT downloaded from the Intel driver download web site) for reference purposes, since we have to assume that the official Windows 7 drivers from Intel for the DN2800MT are the most optimized available. The Tests Test 1 : OS sitting idle at the desktop with USB keyboard and mouse connected, an Ethernet cable connected (with an idle Gigabit link) and the monitor connected via VGA. Test 1b: As Test 1 but additionally with "OS ACPI C3 Report" and "PCIe ASPM Support" enabled in the BIOS (these are disabled by default). Test 1c: As Test 1b but additionally with disconnected Ethernet cable. Test 2 : As Test 1 but additionally with USB keyboard and mouse disconnected. Test 3 : As Test 2 but additionally with monitor switched to DPMS standby via the OS. Test 4 : As Test 3 but additionally with disconnected Ethernet cable. Test 4b: As Test 4 but additionally with "OS ACPI C3 Report" and "PCIe ASPM Support" enabled in the BIOS (these are disabled by default). Test 5 : Linux only - typical 'headless' server configuration - OS configured for runlevel 3 (console mode), text mode boot (no 'rhgb', 'vga=xxx' or 'splash' parameters on the kernel line) with keyboard, mouse and monitor disconnected and only an Ethernet cable connected (with an idle Gigabit link), "OS ACPI C3 Report" and "PCIe ASPM Support" enabled in the BIOS. For all tests BIOS settings are at default values, except as mentioned in each individual test and except for the following: "Serial Port", "Serial Port 2" and "Parallel Port" disabled, "OS ACPI C2 Report" enabled. The Results
Notes and Comments Each test has been repeated at least twice to make sure that the reading is accurate and repeatable. CentOS 6.2 does not have any specific drivers for the CedarView Atom, therefore the higher power draw compared to Windows 7 is expected. CentOS 6.2 installs without any problems on the DN2800MT and automatically selects the generic VESA xorg driver during installation. This means there is no 2D or 3D or video hardware acceleration, therefore it is only suitable for simple desktop use and SD video playback. We would recommend CentOS 6.2 only when using this board as a headless server (for stability and the long term support), not for graphical desktop use. Mageia 2 beta is based on the bleeding edge 3.3.0 Linux kernel, which includes a basic DRM (framebuffer + DRI) driver for CedarView Atoms. The installation works fine, but after the first reboot during the boot the monitor switches itself into standby the moment the DRM kernel driver is activated. After much debugging we figured out that the driver is seeing a ghost FullHD display device on the LVDS port, despite nothing is attached to it. As a workaround appending 'video=LVDS-1:d' on the grub kernel line fixes this issue and allows use of the CedarView GPU with the 3.3.0 kernel. For the tests we have used the 'modesetting' xorg display driver which makes use of the CedarView DRM/framebuffer kernel driver of Linux 3.3.0 MeeGo 1.2.0.6 for Cedar Trail contains both the backported kernel DRM driver and a proprietary binary-only xorg driver for the CedarView Atom from Intel, therefore MeeGo currently has the most complete support for CedarView Atoms among all Linux distros. To install MeeGo we had to append 'video=LVDS-1:d' on the grub kernel line of the install option of the ISO image, as otherwise MeeGo would format the install screens for a FullHD display, which made installation impossible on our 1280x1024 display. Conclusions This board is certainly capable of single digit power draw, at least with certain specific setups. With Linux, running the latest kernel (at least 3.3.0) is recommended to achieve lower power consumption. MeeGo with it's included proprietary xorg driver for CedarView Atoms shows that Linux can achieve similarly low power draw as Windows 7 with an optimized graphics driver. What remains to be seen is if the Linux kernel developers will have access to enough information about the PowerVR SGX 545 GPU core to enable them to incorporate all power saving features of this GPU into the Linux kernel DRM driver. You might also be interested in the following articles:
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