Thanks for the suggestions. Unfortunately, I can't get useful stuff from my logs until it crashes again, so I won't follow that suggestion up just yet (and hopefully not for a while
). IOMMU is compiled into my kernel--i think it's an x86-64 specific option. It allows the addressing of 32-bit PCI when there is more than 4 GB of memory. I only have 2GB but the help option says I should compile it in anyway since it will be disabled if not needed. Indeed, dmesg reveals "PCI-DMA: Disabling IOMMU". IOMMU is not available as a module. I'll try the boot options tonight--the computer is acting as a file server so I can't just reboot at random times.
As for agpgart, there is no option to leave it out. menuconfig just shows "---" instead of a tick box.
#grep AGP .config
# CONFIG_AGP_INTEL_MCH is not set