An anonymous reader writes "Modern Linux desktops like Ubuntu's Unity and the GNOME Shell have placed a requirement on OpenGL 2.0+ support for handling their compositing window managers and desktop effects. Wayland's Weston also needs OpenGL ES 2.0 support. Now with modern Linux distributions like Ubuntu 12.10, rather than falling back to a 2D unaccelerated desktop if you don't have a sufficient GPU or graphics driver, users are being forced to run LLVMpipe as a CPU-based software rasterizer. LLVMpipe works fine if you are on a new PC with a fast x86-64 CPU, but the OpenGL-based Linux desktops are causing growing pains for ARM hardware, virtual machines, servers, multi-seat computers, and of course all older hardware. LLVMpipe is a Mesa Gallium3D driver that uses LLVM for run-time code generation as an attempt at accelerating graphics faster on the CPU. So much for Linux being good for old computers?"
The KMS based graphics stack is already effectively unusable on AGP systems (if you have SMP + AGP, there are race conditions somewhere leading to really hard crashes that appeared a couple of years ago and dozens of years old open bugs with no resolution other than "use PCI mode" which cuts bus bandwidth by 4 or 8 times, and still doesn't work with SMP), but for those with older PCIe/IGP systems you could
always runs Window Maker, Sawfish, Enlightenment, Open Box, or one of many other window managers without a compositor. Of course then you lose compositing, and there aren't any usable external compositors
for some reason. The flipside to this is that moving to OpenGL as the primary interface to the GPU means one fewer driver that has to be written, and will probably lead to an overall improved experience for those with supported hardware given the limited resources Free Software drivers authors have.