Para executar o X com sucesso, acabei usando o driver do OpenBSD com buffer de quadro wsfb
.
para poder fazer isso, criei o arquivo /etc/X11/xorg.conf
com o seguinte conteúdo:
Section "Device"
Identifier "Card0"
Driver "wsfb"
EndSection
De man wsfb
:
wsfb is an XFree86 driver for the OpenBSD wsdisplay frame- buffer devices. This is a non-accelerated driver. The fol- lowing framebuffer depths are supported: 1, 8, 16 and 24, given that the wsdisplay device underneath supports them. A StaticGray monochrome visual is provided for depth 1, all visual types are supported for depth 8 and a TrueColor visual is supported for the other depths. Multi-head confi- gurations are supported.