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Sumo GPU Core

Do not forget that Llano acquired a high-performance graphics core called AMD Sumo. Just like with Zacate processors, the architectural principles used in this core come from the discrete graphics solutions. But considering Llano’s positioning in the market, AMD decided to integrate much more powerful graphics into their new processor with the same number of execution units as in Radeon HD 5570.

In fact, it is true: Sumo is a close relative of the discrete Redwood GPU on AMD VLIW5 architecture. In other words, the highest-end APU in the Llano family will have a graphics accelerator with 400 stream processors, 20 texturing units and 8 raster units. Lower-cost APUs will have one of the SIMD units disabled by the manufacturer and the number of stream processors will be reduced to 320, making the Sumo core more like a Radeon HD 5550.

Compared to the original Redwood, Sumo underwent only two major changes. First, they modified the memory interface to ensure that the GPU can work with dual-channel DDR3 SDRAM via the processor North Bridge and not directly. Work with the memory sub-system is a traditional bottleneck of the integrated graphics cores, so when they put a high-speed GPU inside the new APU, they had to come up with some special optimizations. Unfortunately, Llano doesn’t have anything like Intel’s ring bus and Sumo can’t use processor cache-memory for its own needs. However, it boasts a different feature, which is totally new for a graphics core: it can write directly into the system memory skipping the processor cores. Moreover, all graphics core’s operations with the memory have higher priority in Llano processors than the requests from the computational cores, so they will be processed by the memory controller in the first place.

Secondly, the UDV (Unified Video Decoder) unit in Sumo has been replaced with a newer version. Version 3 of the video decoder in Llano processors supports all popular HD video formats and is compatible with MVC (Multi-View Codec) used for 3D video. So, unlike Brazos, Lynx platform can play 3D Blu-ray via HDMI interface. Moreover, UVD3 is more energy-efficient: it can work independently from the rest of the GPU, which allows turning off stream processors during video playback.

The above described changes allowed AMD to use a 6000-series marketing name for their Sumo graphics core. So, depending on the number of stream processors inside, Llano may have a Radeon HD 6550D or Radeon HD 6530D graphics core.

Integrated analogue of the Radeon HD 5570 graphics card is a pretty tempting offer, but it won’t suit everyone. Therefore, AMD made it possible to upgrade the graphics accelerator inside the APU by using CrossFire technology. In this case this technology is called Dual Graphics and allows pairing the integrated GPU with an add-on Radeon graphics card creating an asymmetrical CrossFire configuration.

The technology is truly impressive, because a Dual Graphics system can take on a graphics card of any type. However, this versatility creates a number of problems. First, you can only improve your graphics performance if the add-on accelerator is no more than twice as fast as the Sumo core integrated into your APU. In other words, if you have a Radeon HD 6850, it would make more sense to use it as a stand-alone discrete graphics card and fully disable the integrated graphics. The second restriction is even more serious. Asymmetrical CrossFire modes work only in DirectX 10 or 11, that is why in DirectX 9 or OpenGL games Dual Graphics won’t improve anything and the performance will drop to the level of the slowest GPU in the system. Nevertheless, Dual Graphics presents not very demanding users with a great way of saving some money, which makes Llano an excellent option for entry-level gaming systems.

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