NVIDIA GeForce GTX 275 Unleashed
The Card, Rel 185, and Ambient Occlusion
The new GeForce GTX 275 looks essentially identical to the GeForce GTX 285 that was released a few months ago--at least on the surface. There are some differences between the two cards, however, that aren't visible without removing the cooling solution.
As you can see, the GeForce GTX 275 has a very similar appearance to the GeForce GTX 285. There are some differences under the hood worth noting, however. The GeForce GTX 275, for example, has a 448-bit memory interface whereas the GeForce GTX 285 has a full 512-bit interface. As such, the GeForce GTX 275 is outfitted with two less memory chips for a total frame buffer size of 896MB, instead of the 1GB available on GTX 285 cards.
The GTX 275's dual-link DVI outputs and HDTV output are unchanged from the 285, and like the GeForce GTX 285 the 275 has an array of ventilation holes alongside the DVI outputs, that run almost the full length of the bracket. There is also a slight curve at the front of the GTX 275's fan shroud where it meets the case bracket, just like the GTX 285.
Looking at the card, you can also see that it is still has a dual-slot form factor and a pair of SLI connectors reside along the top edge of the card. Like the GTX 280 and GTX 285, the new GeForce GTX 275 supports 2- and 3-way SLI configurations.
NVIDIA is also using today's occasion to announce a new feature being implemented in their Release 185 series graphics drivers--Ambient Occlusion. NVIDIA explains what ambient occlusion is thusly: "Standard lighting models compute the color of a surface based on its properties and the lights in a scene. Objects that are in the path of a light cast shadows; otherwise, their presence does not affect the lighting of other objects. Ambient occlusion improves this model by accounting for the dimming caused by objects that block out ambient light. An example of this is the junction where a wall and a ceiling meet; while no direct shadows are cast, the corner nevertheless appears darker. Ambient occlusion simulates this phenomenon, along with all other cases where objects are close enough to block out ambient light."
The two screenshots above show ambient occlusion in action. The top shot is from World in Conflict and the bottom shot is from Half Life 2. In the WiC image, the newly introduced shadows in the grass are immediately apparent. And in the HL2 shot, the shadows along the edge of the ceiling and in the corner by the payphone are the result of ambient occlusion being enabled. The lighting / shadow differences vary from subtle to dramatic, but they definitely enhance the realism of the scene. We should point out, however, that enabling ambient occlusion does have a performance penalty of about 20% - 40% depending on the complexity of the scene, and currently the feature is only supported in DirectX titles.
In addition to ambient occlusion, the Release 185 drivers will offer some performance benefits as well. The Release 185 drivers feature improved texture management in DirectX 10, along with improved Z-culling efficiency, AA compression performance, and enhanced SLI scaling, especially in Valve Software Source-based game engines.
If you'd like to experiment with the new Release 185 drivers, a beta version will be made available on the company's website sometime later today (April 2).