Intel Extreme Graphics

The i845G integrated 3D graphics controller is marketed by Intel as ‘Intel Extreme Graphics’. Intel Extreme Graphics 256 bit core is able to deliver intense, realistic 3D graphics with sharp images, fast rendering, smooth motion and incredible detail. The i845G employs a unified memory architecture (UMA): thus it pumps in the system RAM the memory required by 3D textures when needed. The i845G implements 32bpp graphics allowing true transparency effects and translucent surfaces that’ll help create more realistic scenes with complex shadow effects, smoke effects, clouds, etc. This innovative architecture supports various advanced technologies like the rapid pixel and texel rendering engine.  

The rapid pixel and texel rendering engine utilizes special pipelines that allow 2D and 3D operations to overlap. This engine is able to reduce the amount of memory required for texture storage as well as the memory bandwidth required to read texture memory since it provides a 8X compression. Intel Extreme Graphics includes a non blocking multi tier cache for textures, colors, Z and vertex rendering. Thus within a single pass, the drivers can submit up to four textures to the graphics engine concurrently. The graphics core can switch between 2D and 3D operations even if all the operations of the same mode aren’t yet completed in order ot minimize the overhead time required in switching between modes. Finally a 2D BLT in the RPTR engine now reaches 256-bit supporting fast blitter fill rate. The blitter sequence of the same adresses can access the cache and offloads the memory bandwidth required for the blitter fill rate support. Then the cache is emptied automatically when the sequence of opeartions is over. 

The technology, Intel is the most proud of, is the Zone Rendering. This unique mechanism addresses memory bandwidth limitations by reducing the required bandwidth for graphics. To operate the Zone Rendering technology divides the frame buffer into a number of rectangular zones and then renders all of the pixels within a single zone before proceeding with the next zone. This process highly optimize the use of the render cache. This allows on-chip access for any individual zone to all of the significant color and depth information for a defined frame. That way, it eliminates the need for depth buffer reads and writes, as well as color buffer reads. All of these combined, reduce the maximum theoretical required graphics memory bandwidth. Another benefit of this technique, is that the fill rate isn’t reduced: because pixels aren’t overdrawn in the frame buffer, the fill rate required to draw any scene is equal to the number of pixels in the scene.  

Since memory management is crucial to graphics performance, Intel has developed the Dynamic Video Memory Technology. This technology ensures the most efficient use of system memory allowing up to 64 MB of system memory to be shared between the OS, applications and graphics display. Basically the BIOS dedicated 8 MB of system memory for graphics display: when an intensive graphics application needs more the drivers will request increased memory to the OS. The OS will then grant the request (based on available system memory), and the memory is returned to the OS when the application no longer needs it. 

The  Intelligent Memory Management Technology is another technique to reduce CPU latency and allows longer in-page bursts. It consists of three key elements: Tiled memory adressing capability, Deep display buffer implementation and dynamic data management scheme. The memory addressing allows address remapping in the hardware for all graphics surfaces including textures, frame buffer, Z buffer, and video surfaces. Deep display buffers and dedicated screen refreshes improve visual performance, while the dynamic data management scheme manages burst size and page closing policies for memory accesses. IMM also increases page coherency and improves memory efficiency in texture loads, 2D blitters, color/Z, MPEG2 motion compression, and other operations. 

Intel 845G supports various top notch 3D features like: DOT3 Bump-mapping, point sprites, anisotropic filtering, hardware motion compensation for smooth DVD playback, per pixel fog, etc. When 2D is concerned, you can count on DirectDraw/GDI/GDI+ compatibility, anti-aliased text support, alpha blending, hardware alpha blended RGB cursor, color space conversion, etc. Every features of Intel Extreme Graphics are natively supported by Intel drivers and can be accessed transparently by DirectX 7.0/8.0 or OpenGL 1.1 compatible games/applications. However the famous and great Pixel Shaders aren't supported by this chip which dramatically reduces its interest with recent games.

  
Intel Graphics Drivers (click to enlarge)

During our tests we were very pleased with the 2D quality delivered by the i845G. Unlike its baby brother the i815e, the i845G supports more resolutions and colors (8/16/32bpp) offering an overall higher visual quality which is appreciable with Windows XP and applications like PhotoShop. We didn’t experience problems with recent games and Intel’s 3D engine did a fairly good job to render scenes.

We didn't resist benchmarking the i845G under 3D Mark 2001. The results are quite disapointing. If the integrated Intel graphics controller performs better than its predecessor the i815 it gives results that don't even match a GeForce II MX card. For instance a GeForce II MX is 170% faster than the i845G! The i845G performance are sufficient to run recent 3D games in basic resolutions, but you'll have to forget what anti-aliasing means and what high resolution means. It's clear that with such poor 3D graphics performance the i845G is dedicated to occasional gamers, only. Too bad.