I found an old Matrox Millenium PCI video card, and swapped it into this machine.
lspci reports it as: VGA compatible controller: Matrox Graphics, Inc. MGA 2064W [Millennium] (rev 01) With it, I've been able to boot the 686SMP kernel, and startx with KDE. It's been running all of ten minutes now, but that's ten minutes more than I ever got with the ATI card(AGP). ...so it's looking more and more like this is really a manifestation of the 686/ATI 'random lockup' problem that the fellow at cipherfunk claims to have fixed. I posted his kernel patch here earlier. Here is his patch for the xorg driver. ** Attachment added: "Patch for xorg ati driver" http://librarian.launchpad.net/4309527/xserver-xorg-driver-ati_6.5.7.3-0ubuntu7.diff.gz -- Fail to boot smp kernel https://launchpad.net/bugs/24533 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs