Architecture

Barts, named after the Saint Barthélemy island in the Caribbean, is a performance-segment GPU. It is built on the 40 nm silicon fabrication process at TSMC, Taiwan. Since it is essentially a DirectX 11 generation GPU, most of the components are the same as on the Radeon HD 5000, albeit with a lot of restructuring. The SIMD processing area, like on the Cypress, is branched into two blocks, because there are way too many SIMD units. While Cypress had a single Ultra-Threaded Dispatch Processor component that semaphored instructions and data between the two clusters, with Barts, AMD gave each cluster its own dispatch processor, instruction and constant caches, thus increasing the parallelism. Each cluster holds 7 SIMD engines, with 80 stream processors, each. The computational power of Barts in its Radeon HD 6870 avatar, hence, is over 2 TFLOPS.



There are 56 texture units (TMUs) on Barts, all enabled on the HD 6870, 48 enabled on the HD 6850. With a 256-bit wide GDDR5 memory interface, there are 32 raster operations processors (ROPs). AMD also addressed the one shortcoming of the Evergreen architecture which NVIDIA took advantage of: tessellation performance. Northern Islands GPUs carry a second generation tessellation unit that is both redesigned, and is backed by a new adaptive tessellation algorithm at the driver level. Together, up to 100% increase in tessellation performance is advertised by AMD.



There is a redesigned video acceleration component, the 3rd generation Unified Video Decoder (UVD 3.0), which provides GPU acceleration for Blu-ray 3D and DivX high-definition video formats, and six display controllers offering six TMDS links. This lets users connect up to six displays to as independent display heads, or span display heads across multiple physical displays using the Eyefinity technology. The new HDMI 1.4a connector standard is made use of, which gives you support for stereoscopic 3D standards such as Blu-ray 3D, the two mini-DisplayPort 1.2 connectors support Multi-Stream technology that let you daisy-chain 3 physical displays per connector, letting you wrap up a 6-display Eyefinity array using just those two connectors.