Originally posted by GlowStick
Actually all 3d video cards do that to an extent, and they also do it for the Z plane, withc is objects behind a wall etc, just not as efficnet as a static one.
But PowerVR's idea is they can do a better job of clipping in real time, and they actually did.
Argh, I knew I wouldn't get away with just posting the short answer
Yes, ATI and nVidia both have methods of hidden surface removal which are an order of magnitude less effective than PowerVR's. Not sure if older cards/other manufacturer are using these methods or not. But, PVR proved that deferred rendering can work, it's a shame they don't release some high-end cards.
As a side note to the whole 3dmark thing - It is a common practice for developers to put in their own clip planes to reduce workload. Obviously, nvidia doing it for them (and only for nvidia cards) is not quite the same