I found this interesting article where you are truely seeing the power of the desktops reaching server status.
WITH DUAL core CPUs spreading like wildfire, you can now have affordable real SMP on your desktop - what about taking that same CPU and creating a cheap dual-processor server with an accompanying server-class mainboard?
That's a good question, actually - the current Pentium XE series dual core processors can handle up to four threads at once, with their soon-to-be-extinct Hyperthreading, which makes it quite suitable for entry-level servers in I/O intensive multithreaded workloads like, say, Web serving.
But if you want that advanced I/O, you usually cannot stick with current PC chipsets, at least until most cards are available in PCI Express format. You need PCI-X 64-bit slots still, since many adaptor cards are still mainly using this I/O bus, and the standard PCI is way slow for server grade I/O. Also, you may want to have the flexibility of using either ECC or non ECC memory, depending whether you lean towards extra reliability or lower cost.
A good example of such a board? Well, look at Tyan's entry in this market, the S5162 Pentium 4/D/XE Socket LGA775 server ATX low profile mainboard.
While this is an ATX-sized board, the differences are obvious immediately: three large 64-bit PCI-X slots, all capable of 133 MHz speed, plus one 16X-sized but 8X-speed PCIe slot, low-profile I/O back panel connectors with dual Gigabit Ethernet and XGI onboard VGA output, and on-board flash memory slot show this is not an ordinary desktop board. On the other hand, desktop Pentium CPUs work, both single and dual core, and so does desktop non-ECC DDR2 memory - up to 8GB of it!
The chipset consists of E7230 "Mukilteo" north bridge, with functionality similar to 955X/975X, ICH7R south bridge, and 6700PHX PCI-X bridge. The board's BIOS doesn't provide the desktop-centric performance tuning options, but I did see some good server-centric features like, for instance, console display redirection to a serial port, so your notebook that is connected to that port could then display the boot messages from the board.
I put together a system, checking out three CPUs on this board: the Pentium XE 840 dual-core 3.2 GHz (worked smoothly), Pentium 4 XE 3.73 GHz 1066 FSB (also smooth), and the newest Pentium XE 965 dual-core 3.73 GHz. The last one will probably be fixed soon, by the next BIOS update. While the low-level performance benchmarks in Windows (Sandra, for instance) had results that are nothing to shout about (after all, server boards don't have that many tuning parameters), neither was there a big penalty in CPU or memory-based benchmarks compared to the best desktop boards - with 2 GB of A-DATA DDR2-800 memory, the performance results on both 800 MHz and 1066 MHz FSB were just one to two percent slower than a coof 975X-based mainboard supporting the Intel chips directy.
And oh, by the way, according to the Tyan manual, the Intel south bridge RAID only seems to work in Windows. I didn't have a RAID array on hand to test it with Linux, but I guess the problem is RAID driver functionality in Intel Linux drivers. So, once more, the Redmond Satan has the priority.