A little on the 3870 architecture ...

Before we look at the retail 3870 cards here is a brief overview of the RV670.

The 3870 (RV670) has a lot in common with ATI’s previous high end part, the 2900XT. The core layout is the same as is the number of stream processors (320), texture units (16) and ROPs (16). Features such as tessellation unit are still present as is the use of a ring bus although it differs in specification from the 2900XT. On the older card ATI used a 512-bit Memory Interface and 1024-bit Ring bus, on the 3870 it is a 256-bit memory interface and 512-bit Ring Bus. The use of GDDR4 at higher clock speeds than the 2900 allows the RV670 to cancel out as much of the performance hit from the Bus change as possible. Unless specifically stated by a manufacturer the reference core clock speed of the 3870 will be 777MHz with memory at 2250MHz.

The product begins to differ from previous models in terms of process used to build the GPU's, the 3870 is a 55nm part compared to 80nm used on previous Radeons. The reduction in process also comes with a reduction in transistors, from 700 million down to 666 million and a reduction in power requirements resulting in a card which only requires one 6pin power connector rather than the dual connectors on the XT/Pro. The actual peak power draw on the 3870 is 105w compared to 215w on the 2900 series. ATI have improved power consumption further by improving their PowerPlay technology. When in use the 3800 series will be in one of three modes, 2D, light gaming and intense gaming. The active profile is dependent on the GPU usage with speed/voltage being changed as required. ATI have also taken the opportunity to resolve an outstanding bug, the result being that full 3D speeds are available when playing a game in windowed mode.

ATI have added to the cards specifications in one major area, the addition of DirectX 10.1 support. Whether this is of any benefit to you, the consumer is debateable but it is always nice to know that a card has as up to date a design as possible. Support for more advanced CrossFire has also been added to the 3 series. It will now be possible to link up four cards in a single system and power up to eight displays. This technology goes by the name "CrossFire X" and we are also told that in a future driver support for gaming on multiple displays will be added.

There are two final improvements over the 2900 series and the first is a move to PCI-Express 2.0 (with 1.x compatibility). This gives the 3800 greater bandwidth when combined with the correct motherboard. Also included on each of the new models is ATI’s UVD. We first saw full UVD in the Radeon HD 2400 and 2600 products but unfortunately ATI made a huge error in not including the 2900 series so it is good to have it featured here. There are various benefits which UVD provides; the first is near perfect HD output quality. Next would be full acceleration of Blu-Ray and HD-DVD quality and the final main benefit is the ability to have full screen upscaling of content to 2560x1600.