HyperZ

HyperZ is the brand for a set of processing techniques developed by ATI Technologies and later Advanced Micro Devices and implemented in their Radeon-GPUs. HyperZ was announced in November 2000 and was still available in the TeraScale-based Radeon HD 2000 Series and in current Graphics Core Next-based graphics products.
On the Radeon R100-based cores, Radeon DDR through 7500, where HyperZ debuted, ATI claimed a 20% improvement in overall rendering efficiency. They stated that with HyperZ, Radeon could be said to offer 1.5 gigatexels per second fillrate performance instead of the card's apparent theoretical rate of 1.2 gigatexels. In testing it was shown that HyperZ did indeed offer a tangible performance improvement that allowed the less endowed Radeon to keep up with the less efficient GeForce 2 GTS.
Functionality.
HyperZ consists of three mechanisms:
Versions of HyperZ.
With each new microarchitecture, ATI has revised and improved the technology.