Z Compression — The Z-Buffer is stored in a lossless compressed format to minimize the Z-Buffer bandwidth as Z read or writes are taking place. The compression scheme ATI used on Radeon 8500 operated 20% more effectively than on the original Radeon 256.
Fast Z Clear — Rather than writing zeros throughout the entire Z-buffer, and thus using the bandwidth of another Z-Buffer write, a Fast Z Clear technique is used that can tag entire blocks of the Z-Buffer as cleared, such that only each of these blocks need be tagged as cleared. On Radeon 8500, ATI claimed that this process could clear the Z-Buffer up to approximately 64 times faster than that of a card without fast Z clear.
Hierarchical Z-Buffer — This feature allows for the pixel being rendered to be checked against the z-buffer before the pixel actually arrives in the rendering pipelines. This allows useless pixels to be thrown out early (Early Z Reject), before the Radeon has to render them.