I remember Carmack talking of this.
That was not due to the card being clever enough to throw out whole polygons very early. This technique exists, but requires a hierarchical z-buffer, a bit like a mip map. It's been a while since I didn't check very deep the sepecifications of newest cards, but I'd be surprised they include such a buffer (amybe another technique, don't know). And above all I'm sure they didn't at the time Carmack talked of this.
At that time the speed up was more due to fill rate considerations: if you draw front faces first then the next triangles will much more often fail the z-depth test (which means less pixels that need to be written in the frame buffer) than when drawing back to front.
That was not due to the card being clever enough to throw out whole polygons very early. This technique exists, but requires a hierarchical z-buffer, a bit like a mip map. It's been a while since I didn't check very deep the sepecifications of newest cards, but I'd be surprised they include such a buffer (amybe another technique, don't know). And above all I'm sure they didn't at the time Carmack talked of this.
At that time the speed up was more due to fill rate considerations: if you draw front faces first then the next triangles will much more often fail the z-depth test (which means less pixels that need to be written in the frame buffer) than when drawing back to front.