Pentium M for the Desktop: AOpen i855GMEm-LFS & DFI 855GME-MGF

CPUs|Motherboards
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The 855 MCH supports up to 400 MHz front side bus speeds, pedestrian in these days of 800 MHz and 1066 MHz FSB. The 855 chipset allows a maximum of 2GB DDR memory on two DIMM slots and only supports single channel DDR-333 memory. This limits peak memory bandwidth to 2.7 GB/sec. In contrast, P4 boards with dual channel DDR2-533 have memory bandwidth levels of 8.6 GB/sec.

The ICH4 Southbridge is a bit dated, as it was the common I/O controller hub for second generation P4 processors on 845 chipsets. While the ICH4 supports PCI, USB 2.0 and IDE storage, other features such as S-ATA, RAID, PCI Express slots, or HD Audio are not found in this older chipset. AOpen had to go with third party hardware to fill out the feature set. A Promise S-ATA II controller chip supports two S-ATA hard drives in standard RAID-0, RAID-1 or JBOD modes. Because the chip is S-ATA II compatible, it also supports Native Command Queuing and Staggered Spin-up.


ICH4 southbridge chip. Also note SATA-II, USB 2.0 and Firewire headers at bottom of board.

The onboard audio supports basic AC'97 audio through a Realtek controller for 5.1 analog audio output, but no digital output. The motherboard itself contains the pinout for a SPDIF digital connection but there is no hardware for external connection to the ports.

The board also features built-in Firewire 400, but no external ports on the I/O panel or PCI slot hardware are provided. There is an Agere Firewire 400 controller, which is output only through two Firewire pinouts. This allows you to connect remote front or back panel Firewire ports. One nice feature is the colored front I/O header, which makes it easy to hook up the front panel wiring when the board is installed in the case.


Front I/O header is color coded.

The board's AGP slots is only 4x but it can still run modern AGP cards like the Nvidia 6800 and Radeon X800. Today's fastest AGP cards rarely reach the bandwidth limits of AGP 4x, so this is not much of a limitation. Also included are three 32-bit PCI slots, which is standard for a m-ATX board.


An AGP slot and some spare PCI slots!
This unique concept makes this board useful to the home user compared to early industrial P-M boards.

Being the "G" version of the i855 chipset, the board also includes Intel's integrated Extreme Graphics 2 onboard video, suitable for 2D applications but not up to snuff for 3D gaming or anything multimedia intensive.

The board is equipped with two Marvell Gigabit LAN controllers. These chips run off a 32-bit PCI bus, so they may not be as efficient as a CSA controller, but they should be sufficient for most applications.

The ATX I/O panel includes the usual group of PS/2 mouse & keyboard connectors, as well as a parallel and serial port, HD-15 VGA connector, the four USB 2.0 ports, dual LAN ports, and the three multifunction analog audio jacks. As noted earlier, there is no external Firewire port or external SPDIF connector on the I/O panel.


AOpen provides all the typical I/O connectors along with an extra GigE LAN port.

The board is powered by a standard 20-pin ATX plus an auxiliary 4-pin 12V connector. Since real-world power consumption of these Pentium M CPU's is so low, power supplies rated as low as 250W would be plenty for a system such as this, even with a power-hungry GeForce 6800 vidcard installed.

Our board came with these accessories:

  • low profile CPU cooler
  • SATA data cable
  • pre-folded flat ribbon IDE cable
  • pre-folded floppy ribbon cable
  • SATA power adapter
  • ATX I/O shield
  • Promise RAID drivers on a floppy
  • CD with drivers and utilities
  • well written user manual.

AOpen doesn't highlight its most interesting utility, the Series Tool, which lets the user control the CPU FSB and multiplier as well as the speed of the CPU cooling fan from within Windows. It also features a "SpeedStep" mode which works with the CPU's architecture to dynamically adjust the multiplier up or down in concert with the CPU load .

There is a manual setting to preset a series of speeds for the CPU to run depending on the load. The "Fan Control" setting allows one to set the fan speed to full speed, a fixed speed that is some percentage less than full, or an automatic mode based on temperature parameters set by the user. The tab marked "Overclocking" surprisingly enough, let's you overclock the CPU by adjusting either the multiplier or the FSB. A "Hardware Monitor" tab keeps track of the CPU and system temps, as well as the system voltages. There's little documentation about this tool on their website and nothing at all in their manual.



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