> Section "Device"
>     Driver      "r128"
...
> (--) PCI:*(0:16:0) ATI Technologies Inc Rage Mobility L AGP 2x rev
> 100, Mem @ 0x91000000/24, 0x90000000/12, I/O @ 0x0400/8, BIOS @
> 0x90020000/17
...
> Fatal server error:
> no screens found

Rage Mobility is not a Rage 128, it's a Rage Pro based chip. The Rage128
driver does not support it. Driver ati would normally suffice, but I
think 2.1 shipped without the ati_misc driver that supports
Mach32/64/Rage/Rage Pro chips. If you had a Rage Mobility 128 this would
be a different story, but I don't think they switched to that until the
Pismo.

> Fatal server error:
> xf86MapVidMem: could not mmap screen [s=20000,a=a0000] (Invalid argument)
...
> (don't know much about other archs than x86, but the segment 0xa000
> and the INT 0x10 brings back memories of the old days of VGA/SVGA
> programing for MS-DOS and OS-Independent DEMOs, isn't the XFree
> thinking that the ibook is an x86 machine?)

Pretty much, but I know even less about it than you do.