AOpen i915GMm-HFS: 2nd Gen Pentium M desktop board

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The board is a micro-ATX form factor, in keeping with the all the Pentium M motherboard releases to date. Given the very complete feature set and the size of the board, the 915Gmn will be a prime candidate for HTPC and SFF desktop systems.

The board itself features the AOpen standard black PCB, as well as the fancy aluminum "AOpen" heatsink, although this time it appears on the southbridge instead of the northbridge. The most obvious thing about this new board is the positioning of the components on it. The CPU, NB chipset and DIMM slots are all in non-standard locations, making this board look like a strange cross between an AMD A64 board, and a BTX offering. Why AOpen laid it out this way, I don't know but it doesn't seem to interfere with its installation or operation.


NB heatsink at center of board. It's actually larger than the CPU heatsink!

The board is dominated by the big aluminum northbridge heatsink positioned near the center of the board itself. The processor socket is located to the right of the NB and is sandwiched in between the NB heatsink on one side, the voltage regulators and IDE header on the opposite side, and a pair of jumpers near it's bottom side. This doesn't leave much room for a CPU heatsink, a fact that is clearly evident by the tiny, apparently proprietary set heatsink mounting holes located around the periphery of the CPU socket. The CPU socket is the same low-profile "twist-lock" notebook type that was found on AOpen's earlier 855G board.


Close quarters around CPU socket.
DIMM slots and caps above, Vreg on right, jumpers below.

AOpen's earlier 855G board used a standard Pentium 4 heatsink bracket, and included their own cooler that easily installed onto the P4 bracket, which did a good job of cooling the CPU fairly quietly, especially if run at under 12V. AOpen has made big changes to that system for their latest P-M board. Whether due to space constraints around the socket, or perhaps a marketing-based decision, this board includes a small 18 fin aluminum heatsink and a 40 x 10mm fan. This combination is smaller than a lot of northbridge heatsinks that I've seen, but perhaps AOpen considers it enough to handle the low 20-25W output of a Pentium M CPU. The heatsink is mounted by bolting it down onto a metal bracket that fits beneath the motherboard and correct pressure is provided by a set of four spring-loaded screws.


AOpen heatsink package. Insulated steel bracket goes underneath the mobo.


Yup, this CPU HS actually seems to have less cooling surface area than the HS on the NB chip.

The DIMM slots are located above the processor and northbridge, as in the newer AMD A64 boards. I'm not too sure of the engineering behind this layout, but it certainly doesn't mean that Intel/Aopen have moved the memory controller on die like the A64. The blue set of DIMM slots supports up to 2GB of DDR333 memory, the black set supports up to 2GB of the new DDR2-533 memory, with a theoretical bandwidth almost three times greater than that of the DDR333 slots. The DDR2 memory does operate at higher latencies than typical DDR memory, and whether the Pentium M can even use all the extra bandwidth provided by the DDR2 is another issue. It's nice for the end-user to have a choice though. As DDR2 becomes more mature and penetrates more widely into the marketplace, the inclusion of the DDR2 slots could be a nice -- even necessary -- feature.


DIMM slots. Black for Dual Channel DDR2, blue for good 'ol DDR.

The upper left corner of the board sports a standard 20-pin ATX connector, as well as the AUX12V power connector. Below the ATX connector lies the sole P-ATA header on the board. The 915GM chipset only supports one standard UATA channel, which limits the user to no more than two non-SATA devices. This may not be too much of an issue though since the ICH6M southbridge includes support for two SATA-1 devices, and the integrated Silicon Image controller provides a pair of SATA-II ports, which can support a RAID 0 or 1 configuration, or be used as JBOD to add another two SATA devices to the system. The SATA-II ports also support NCQ.


SATA and SATAII ports and color coded front I/O connectors, plus southbridge heatsink.

Continuing clockwise around the periphery of the board, we find the I/O header for the Power and Reset switches, and the power and HDD activity LEDs. These are color coded, just like on the previous AOpen Pentium M board; it's a feature that I really appreciate. Next up are a pair of internal Firewire headers, run by an Agere 1394 chip, and two pair of internal USB 2.0 headers, for a total of four internal USB 2.0 channels.


Internal headers. From L to R: FDD, COM 1 & 2, Parallel, 2 x USB 2.0 and 2 x Firewire.



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