What about an ARM chip with nothing more than a raw segment of memory and a blitter?
The framebuffer is the final landing point before hitting the CRTC/DAC.
The other important question to ask here is, which framebuffer?
In certain circumstances such as a machine I have with an onboard IPMI2.0 compliant baseboard management controller integrating a matrox g200 core & IPKVM, as well as a PCI express graphics card I tossed in to support my 90 degree LCD setup.
The kernel seems to prefer to use the matrox, but X has always popped up on the Radeon 2600xt card.
I realize I'm sort of splitting hairs here, but the semantics can be way different.
Edit: Gah, forgot about G3d's softpipe. Sorry 'bout that.