Below the Surface, About the Engine...

Time to dig a bit deeper, and see what lies beneath the cooling system of the Jetway Radeon HD 2900 XT graphics accelerator. We are taking a look under the hood by pulling of the cooling solution. As you know by removing the cooling system you are voiding the warranty. For those who don't care about the warranty and want to see what's underneath, with proper handling the heatsink can be removed for what ever reasons. Our reason is plain and simple, what engine is powering the Radeon HD 2900 XT and which other components are present. We don't recommend it however, but we did want to share the real stuff that makes the XT what it is today.

Once the screws have been removed, the heatsink can be taken of and the full scale PCB sees the light. We must admit that we were a bit surprised as the main weight of the Radeon HD 2900 XT comes from the cooling solution alone. Most electronic components have been invisible from the start on the front side of the PCB. Only some smaller components were not covered by the heatsink. All other main components like the GPU, voltage regulators and memory chips however can only be seen once the cooling solution was taken off. A rather complex view, with more components than we would have guessed, though the looks are somehow familiar.

The Jetway Radeon HD 2900 XT is powered by the R600 series line of graphics processors, set at 742MHz clock speed. The R600 version on the Radeon HD 2900 XT is a complete new chip, build from scratch to meet the DirectX 10 requirements and completely towards the unified shader logic. The R600 chip uses an 80nm manufacturing process for its high performance circuits, which eradicate limitations with both frequencies and higher heat dissipations. Notice as well that the GPU die is protected against damage with a traditional metal frame, but that the inner core is rotated giving it a rather strange look. And next to that the inner die is completely blank, where we normally find some details on the type of chip and when it was manufactured.

	GeForce 8800 GTS	Radeon HD 2900 XT
Core Speed	513MHz	742MHz
Memory Speed	1584MHz	1656MHz
Shader Clock	1188MHz	743MHz
Stream Processors	96	320
Memory Size	640MB GDDR3	512MB GDDR3
Memory Interface	320-bit	512-bit
HDCP Support	Compliant	Compliant

With the introduction of the R6x GPU's we see a new era being kicked off which is all about the unified shader technology. To incorporate this within the Radeon HD 2900 series we see that ATI has come up with the stream processors which can be used in a unified way as either vertex or pixel shader. That means that these are no longer fixed to just being a vertex or pixel shader, but their function changes according to the processing needs. With a unified GPU architecture some bottleneck between pixel, shader and geometric processing is reduced to a great extend. The Radeon HD 2900 XT shares the same full 512-bit external ring bus memory controller. This quite advanced ring bus technology that ATI developed within the R600 core comes with a great memory bandwidth that can be used to process a substantial amount of data.

The Jetway Radeon HD 2900 XT comes with eight memory chips in total which are all located on the front side of the board. The memory chips are placed strategically around the R600 core. Each of these memory chips gives their heat away to the coolers copper sole via elastic rubber-like thermal pads. By cooling the memory chips on their own, it provides extra protection towards the lifetime of the chips in general. The ram chips are placed two by three by three and give a total of 512MB memory. Some brands went one step further and equipped the Radeon HD 2900 XT with 1GB memory, which might have an impact on the PCB and the location of the chips around the graphics card.

In total the Jetway Radeon HD 2900 XT features 512MB GDDR3 memory which is running at 1.65GHz, following the reference settings by ATI. In essence that would mean that some decent 1.2ns memory chips would be just fine for the job. However ATI has opted for faster Hynix GDDR3 memory chips, which will allow some extra freedom for the different manufacturers. These Hynix GDDR3 chips come marked as 1.0ns access time and are therefore rated at 2.0GHz frequency and operating at 1.8V. Being set at only 1.65GHz leaves some margin for some overclocking. These chips are known to go really fast, and offer great overclocking potential however we need to take into account that these chips require 2.2V to operate at clock speeds higher than 1.8GHz, but can at that point reach 2.0GHz and even more.

Just to the left of the R600 core we have the ATI Theater 200 chip, which we haven't seen before as is was covered by the massive cooler. The ATI Theater 200 chip provides the Radeon HD 2900 XT with various video capabilities enhanced by the Avivo HD technology. This video and audio decoding chip is used in the Radeon HD 2900 XT to provide Dolby Digital 5.1 audio to HDTV's through a HDMI adaptor that runs off a DVI port. Well that's about it on the insights of the Jetway Radeon HD 2900 XT graphics card, I guess it is time to put this one to work and show some of the performance figures. So we will just reassemble it again, applying some new thermal compound and stick it into our test system.