2. The 2700G Multimedia Accelerator

The operation of the 2700G Multimedia Accelerator is best explained by taking a look at the block diagram of the chip and the PDA system platform.

Block diagram of the 2700G

From this you can see that the 2700G is a graphics chip that adds 2D and 3D accelerator functions to the PDA. Other special attractions include a small on-die video memory - 704 kB for the 2700G5, or 384 kB for the 2700G3 - and dual-display mode.

In order to enable 3D acceleration, the component features a rendering pipeline implemented as dedicated hardware. Intel claims that it can process 831,000 triangles per second with a pixel fill rate of 84 million pixels - values that look rather modest compared to those of even halfway modern graphics cards . Besides 2D functions such as alpha blending and 2D clipping, the chip supports 3D functions including:

Texture and light mapping Bilinear, trilinear and anisotropic texture filtering Texture compression Smallscreen, offscreen and backface culling Fullscreen antialiasing

The video accelerator unit of the 2700G also handles the computation-intensive work of decoding MPEG1/2/4 and WMV videos, handling inverse zig-zag, inverse discrete cosine transformation and motion compensation. That not only helps lower the CPU load, freeing up extra capacity for other tasks, it also reduces the system bus load. During video playback, for example, the motion compensation is calculated in the 2700G's memory, so the operation doesn't tax the system bus.

Video accelerator unit of the 2700G

Block diagram of a PDA consisting of a PXA27X CPU and a 2700G graphics/video accelerator