crappy hardware
I've come to the conclusion that most consumer retail motherboards suck to varying degrees. Some of them are just horrific abominations that are poorly designed, poorly built and/or poorly tested. Some examples (with their identities hidden to protect the guilty):
* We had this mid-range quality motherboard in a system that was completely locking up roughly every 48 hours with nothing logged. This board was less than 3 months old. Replacing it fixed the problem. So clearly it was crappy quality
* I had this lower end board with 3 PCI slots. If I put a PCI Intel 100Mb NIC into one of the PCI slots, it never showed up on the PCI bus at all. If I inserted it into a 2nd slot, it appeared on the PCI bus, but just didn't work at all (100% packet loss). Only in the 3rd PCI slot did it work properly. Crappy BIOS? Crappy board?
* Another lower end board (different model than the previous one). If I disabled the onboard NIC, and inserted a PCI Intel 100Mb NIC, the system would lock up at the end of POST, before handing off to booting the OS. It was so bad that I couldn't even get back into the BIOS to re-enable the onboard NIC, and removing the Intel PCI NIC also had no impact. Once in this end-of-POST lockup state, it remained that way unless I pulled the CMOS battery to reset the BIOS altogether. Complete crap BIOS.
I've got many more examples, but those are some of the better ones. I'm sure that some will argue that I'm being unrealistic. I'm using Linux, which is just about never a consideration for consumer motherboards, and I'm using them for computing, rather than leisure/gaming. Its just a pity that people generally have such low standards for their hardware. I suspect that many others trip across these problems, but most hardware vendors are either unaware, or just don't care, because its not a significant portion of their customer base.