GammaChrome Features
S3 haven't given out lots of architectural details of the inner workings of the chip, however we can have a look at some of the main features that are available on boards based on the GammaChrome architecture:
- DirectX9.0
S3 Graphics 3rd Generation Chrome Graphics Processor with:- Vertex Shader 2.0
FP32 precision Vertex Shaders - Pixel Shader 2.0
FP24 Pixel Shaders - 16 textures per pass
- Additional Optional DirectX9.0 Feature support
- Shadow Volume Acceleration with 2 sided stencil support
- Non power of 2 textures
- High accuracy floating point render targets for cinematic quality image rendering
- Volume and cube maps for photo-realistic reflections
- Programmable per pixel gamma correction
- Vertex Shader 2.0
- Native PCI Express
- 1.0A PCI Express Compliance
- 16, 8 and 1 lane configuration support
- "Hi-Def Experience"
- HDTV Encoder supporting 1080p and all 18 ATSC HDTV and SDTV standards
- Component (YPBPr) output
- 4:4:4 conversion with 10 bit DAC resolution
- Full desktop view in HDTV mode
- 480i standard TV output (S-video, composite)
- Macrovision compliant
- 2/3 tap flicker filter with programmable coefficients
- NTSC/PAL support for standard TV mode
- Vertical over/under-scan compensation
- 2X Over-sampling for premium image quality
- Adaptive aperture correction
- Full range RGB to YUV color space conversion with Hue, Saturation and Contrast adjustment
- Smooth vertical overscan compensation with programmable contraction factor
- "DeepColor Precision"
- 10-bit per component RAMDAC
- "Chromotion 2.0" Programmable Video Engine
- Microsoft DirctX-VA compatible programmable video engine for playback acceleration of codecs such as Windows Media Video, MPEG-2, MPEG-4, DiVX and others.
- Post Processing filters such as de-blocking and smoothing
- IDCT Hardware Support
- Motion Compensation
- 4x4 programmable kernel filter video scaling
- Per pixel adaptive de-interlacing
- Real time post processing
S3 have decided not to include Shader Model 3.0 capabilities, and in fact have said they will circumvent it entirely going straight to Shader Model 4.0 when that is finalised, so the S18 configuration features 4 VS2.0 vertex shaders and 4 rendering pipelines, each with PS2.0 fragment shading capabilities. The fragment shaders are said to be beyond the base limitation of PS2.0, but at present we are not aware of any HLSL profile available for it so while that remains the case developers can only treat it as having base PS2.0 capabilities. The pipelines are largely inherited from the DeltaChrome architecture, however the fragment shader ALU's have been increased a little to run everything at FP24 precision at full speed, removing any reliance on FP16 instructions.
Part of the point of GammaChrome's introduction was for S3 to create and entrant into the PCI Express market, and as such GammaChrome implements a PCI Express for Graphics 16 lane host interface, however it can operate in 16x, 8x or 1x lane modes. As with ATI's PCI Express implementation, and useful for power saving environments such as mobile configurations, the number of active lanes can by dynamically switched such that is in power saving modes it can drop back to a single lane and then rise back to 16 lanes when needed, without a reset.
GammaChrome's memory bus is still limited to DDR, which puts its maximum frequency at the 450MHz range, where mass production GDDR memory really halts. The total bus width is 128-bit, but can also operate at along 64-bit for lower end models, and the supported memory sizes are from a minimum of 32MB to a maximum of 256MB. In conjunction with the PCI Express bus the chip also has what S3 term as "ChroMAT" memory address translation, however this appear to fall short of ATI and NVIDIA's HyperMemory/TurboCache solutions as S3 only detail texturing from main memory and not (pixel) rendering.
In keeping with the focus on video capabilities this chip has S3 have also included a Video Input port for compatibility with a wide range of Tuner / Video Decoder devices for multimedia solutions.
