http://www.imgtec.com/PowerVR/Produc...hics/index.asp

Specifically:

"PowerVR cores use an on-chip tile buffer to keep all bandwidth-intensive pixel processing on-chip, where it can be executed most cost effectively and efficiently.

Memory bandwidth requirements are minimized by eliminating all Z-buffer traffic between the 3D core and external memory, and by ensuring that only visible pixels are ever written to the frame buffer. "

So, no reason to expect it not to work on something like the N800/N810 with an external framebuffer.

Though it does ask the question of whether or not the last sentence is to be interpreted literally, in which case the data would need to be copied from the 5Mbit omap on-chip framebuffer to the lcd controller framebuffer.