Intel's New DDR Chipsets - 845E & 845G

There are three memory related features that the 845G core is outfitted with. The first is what Intel calls Dynamic Video Memory Technology, which is a fancy way of talking about how the graphics core allocates memory for its own use. Since the core has no dedicated "local" video memory, it must block off a section of system memory for its own use. The conventional way of doing this is to set a certain size in the BIOS (e.g. 8 - 64MB) and that part of your system memory is blocked off only for use by the graphics core. As you can probably guess, that's a very wasteful approach since most of the time (in 2D situations at least) you aren't using anywhere close to that full amount. Intel's approach makes a lot of sense; the graphics controller (GMCH - Graphics and Memory Controller Hub) sends a request to the driver to allocate non-swappable, non-cacheable memory pages for graphics. Since the GMCH doesn't use AGP GART, rather its own translation tables for the memory addressing the pages don't have to be physically contiguous in the memory space. The GMCH won't block off a set size of memory, instead it will allocate a minimum amount of memory (0.5MB) and whenever an application demands more it will dynamically resize the allocated memory to compensate. This is designed to maximize system performance while using the integrated graphics controller by freeing up as much system memory as possible. For OEMs that want to advertise that their systems have 32MB or 64MB of graphics memory, they can select a minimum amount of memory to set aside for the GMCH. Doing this doesn't help performance any and actually it hurts performance since it makes the GMCH act a lot like a conventional SMA graphics controller, allocating more memory than it actually needs for the sake of being able to advertise large memory sizes.

When it comes to memory bandwidth efficiency the remaining two technologies come into play. Intel's Intelligent Memory Manager Technology defines a new way of addressing memory for the GMCH; there's not much information on how the technology actually works but it splits the allocated memory up into squares or tiles and manages to decouple the front and back of the rendering engine in order to optimize the graphics data to be provided in a very DRAM-friendly manner. This is another measure Intel took in order to make sure that the use of a SMA graphics core would not adversely impact overall system performance (at least noticeably).

Intel's Zone Rendering Technology

Finally there is Intel's Zone Rendering Technology; this technology actually effects the manner in which 3D scenes are rendered and optimizes the rendering process for the GMCH's internal caches/buffers in order to improve memory bandwidth efficiency. At the end of the single rendering pipeline there is a fairly large cache for colors/Z-values. As data comes through the pipeline the zone rendering engine sorts the workload (triangles) in order to fit within the cache. During the actual rendering, the scene is rendered one zone at a time but since a lot of the color/Z data is now located within the chip's cache a lot of bandwidth can be saved (e.g. reads/writes to the Z-buffer).

In terms of features that are supported by the new graphics core, things like non-power of 2 texture sizes are important as they will be necessary for Microsoft's next-generation OS (Longhorn) that is supposed to make considerable use of 3D in its UI. Texture compression is supported in the form of DXTn and FXT1 which is another first for an Intel graphics core (although the rest of the graphics world has had it for years now). There is also a lot of logic included in the design that aids in switching between 2D and 3D modes which isn't very important for most uses of the graphics core but could come in handy with future OSes.

When combined with the 845G chipset there is still an external AGP 4X slot that you can populate with an add-in card for higher 3D performance. The 845GL however does not feature an external AGP slot which is the only difference between the two chipsets.

In terms of performance, the 845G graphics is comparable to a GeForce2 MX 200 which isn't a very high level of performance at all. Intel expects to stick to their current graphics release schedule in that they will be releasing an updated graphics core every two years. With a big push towards raising the bar in terms of 3D performance before Longhorn ships, we'd think that Intel would have to do a bit more than what they've done with the 845G's graphics in order to truly raise the performance bar. At least when the i740 came out it was a competitive part, but unless Intel invests some serious time and effort into the graphics market then it will be difficult for them to stand up in such a competitive arena.