Comment 17 for bug 248438

Here's what we'd add to the driver's quirks table:

    /* Intel 82852/82855 host bridge / Mobility 9600 M10 RV350 Needs AGPMode 1 (deb #467460) */
    { PCI_VENDOR_INTEL,0x3580, PCI_VENDOR_ATI,0x4e50, PCI_VENDOR_ACER,0x0061, 1 },

    /* Intel 82865G/PE/P DRAM Controller/Host-Hub / Radeon Mobility 9800 Needs AGPMode 4 (deb #462590) */
    { PCI_VENDOR_INTEL,0x2570, PCI_VENDOR_ATI,0x4a4e, PCI_VENDOR_DELL,0x5106, 4 },

    /* VIA VT8377 Host Bridge / R200 QM [Radeon 9100] Needs AGPMode 4 (deb #461144) */
    { 0x1106,0x3189, PCI_VENDOR_ATI,0x514d, 0x174b,0x7149, 4 },

Debian #467235 didn't have lspci output or an Xorg.0.log attached, so I dunno what the host bridge is in that case.