GPU Compute and New AA Modes
In addition to the new features we mentioned earlier, the Radeon HD 6900 series core offers a number of GPU-Compute and Image Quality related enhancements as well.
Cayman's GPU Compute Architecture
The Radeon HD 6900 series GPU’s compute enhancements include asynchronous dispatch support, which allows the chip to execute multiple compute kernels simultaneously with each kernel having access to its own command queue and protected virtual address domain. The GPU also sports dual bi-directional DMA engines for faster system memory reads and writes and the chip is capable of coalescing shader read ops. It can also fetch direct to local data stores within on-chip memory with faster flow control and faster double precision ops, which are 1/4 of the single precision rate.
The Radeon HD 6900 Series' New EQAA Modes
New enhanced quality anti-aliasing modes, EQAA, are set to debut with the Radeon HD 6900 series as well. The new modes offer up to 16 coverage samples per pixel and the color and average samples can be independently controller. EQAA also offers custom sample patterns and filters, and the new modes are compatible with Adaptive, Super-Sample, and Morphological AA modes. EQAA should offer better image quality than standard MSAA modes (by all rights), but with a similar memory footprint requirement.
The 6900 series also has the new anti-aliasing mode that debuted with the Radeon HD 6800 series as well, Morphological AA. The Morphological AA feature is accelerated using DirectCompute and delivers full-scene antialiasing, but at speeds much faster than super-sampling. It is compatible with any DX9, 10, or 11 applications and is switchable via the Catalyst Control Center. Like the Radeon HD 6800 series, other enhancements to the Cayman / Radeon HD 6900 series GPU included a new Unified Video Decoder engine, bringing it up to UVD 3. The only major change here is that the new architecture can now accelerate DivX and xVid files as well. The Radeon HD 6900 series also features HDMI 1.4 and DisplayPort 1.2 support. They also support a new power clamping technology dubbed PowerTune.
PowerTune utilizes a control processor integrated into the Radeon HD 6900 series to monitor GPU activity in real-time 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.