X fails to start without an xorg.conf on i810, because the default depth set by the server (32) is not supported by the driver.  I think the driver should default to 16 bits (it supports 24, but when I tested it that didn't seem to work very well, and dri is disabled at 24 bits depth anyway) instead of letting the server use 32 and failing later on.

diff --git a/src/i810_driver.c b/src/i810_driver.c
index 1ecb04a..53121a6 100644
--- a/src/i810_driver.c
+++ b/src/i810_driver.c
@@ -954,7 +954,7 @@ I810PreInit(ScrnInfoPtr pScrn, int flags)
    pScrn->monitor = pScrn->confScreen->monitor;
 
    flags24 = Support24bppFb | PreferConvert32to24 | SupportConvert32to24;
-   if (!xf86SetDepthBpp(pScrn, 0, 0, 0, flags24)) {
+   if (!xf86SetDepthBpp(pScrn, 16, 0, 16, flags24)) {
       return FALSE;
    } else {
       switch (pScrn->depth) {