28nm Tahiti: New GPU Features
In addition to featuring a totally new GPU architecture, Radeon HD 7900 series cards like the Radeon HD 7970 also sport a number of new features and support for new graphics technologies.
AMD’s ZeroCore Power Technology is one that’s going to please many hardcore gamers. As it stands today, when multiple cards are configured in a CrossFire configuration, all of the cards remain powered up, generating heat and noise. With ZeroCore Power Technology, however, when not gaming (or running an app that can leverage multiple GPUs), companion cards can actually be powered down to the point where their fans can stop spinning. When ZeroCore Power Technology kicks in, idles cards consume about 3w of power, with only about 1w going to the GPU.
As we mentioned earlier, the Radeon HD 7900 series cards are also outfitted with the latest iteration of AMD’s hardware tessellation units. The tessellators in the 7900 series are still limited to 2B verticies/s, but efficiency improvements have been made along with enhancements to off-chip buffering and caches. The end result is improved performance at all tessellation factors with up to a 4x improvement in throughput versus the Radeon HD 6900 series.
Another new feature coming with the Radeon HD 7900 series is Partially Resident Textures, or PRT. Games and applications will need to be specifically coded to take advantage of PRT, but when they do, they’ll be able to essentially stream in texture data on demand. PRT textures are chunked into 64K tiles and the tiles that need to be resident in GPU memory are streamed in when necessary, in lieu of loading entire textures. When and if used properly, PRT should be able to help minimize or eliminate the stuttering that’s sometimes caused on texture loads.
Radeon HD 7900 series cards will also feature a new integrated audio codec and offer support for discrete digital multi-point audio. The Radeon HD 7900 series can support as many audio streams as there are active displays connected to the cards. What the technology does is allow for audio to seamlessly follow video as it is dragged from screen to screen. This video can come in handy for multi-display video conferencing where each participants audio is played only through the speakers on the screen on which his image is being displayed or in any scenario where video and audio is being played on one screen and not necessarily the other.
Also returning with the Radeon HD 7900 series is AMD’s PowerTune technology. PowerTune utilizes a control processor integrated into the Radeon HD 7900 series to monitor GPU activity in real-time at the micro-second level and dynamically adjust clock speeds to enforce a hard TDP ceiling. PowerTune offers direct control over the GPU’s power draw and no longer needs to constrain default clock speeds to accommodate “power virus” type applications. We should also note that PowerTune is controllable via AMD’s Overdrive utility should users want to tweak performance based on their cooling and power configurations.
A number of new features are coming to Eyefinity as well. AMD is unifying their stereo 3D support and Eyefinity so that any game that works across three monitors will also work in 3D mode as well. This feature will be enabled on both 7000 and 6000 series Radeons. In a driver update scheduled for February, custom resolutions will also be supported, there will be improvements made to the preset managers, and taskbar positioning is coming as well.
With Catalyst 12.1 user editable CrossFire and 3D profiles on a per application basis were made available. And when Windows 8 ships next year, AMD will provide a unified driver for Vista, 7, and 8 systems, with Direct3D 11.1 support scheduled for a future driver release that will arrive sometime after Windows 8 ships.