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RADEON X850 XT CrossFire Edition Graphics Card

The RADEON X850 XT CrossFire Edition (left) doesn’t differ from ordinary RADEON X850 XT/XT Platinum Edition (right) externally, at least until you remove the cooling system.

 

 

One thing will catch your eye immediately: there is no S-Video connector and there is a DMS-59 connector instead of one DVI output. On a closer inspection you can notice a chip under the cooler which is missing on the ordinary RADEON X850 XT – the above-mentioned single-link TMDS receiver TFP401A from Texas Instruments. The remaining components of the frame-combining system are located under the cooler. Some differences can be seen on the reverse side of the PCB, too. There is no spot for a VIVO chip Rage Theater – there’s wiring pertaining to the Compositing Engine there, instead. There is also a 14-pin connector at the top of the PCB, probably for engineering purposes. It maybe serves for pre-programming the Xilinx matrix.

More points of difference rise up if you remove the cooler:


RADEON X850 XT CrossFire Edition


RADEON X850 XT/XT Platinum Edition

The left part of the PCB is all occupied by the Compositing Engine chips, the heart of which is the programmable matrix Xilinx Spartan-3. A 330MHz RAMDAC is located above it. To the right of the RAMDAC there is a TMDS transmitter that outputs the image on TFT panels with a DVI interface. The TV output controller integrated into the GPU is not used due to obvious reasons, and the developers didn’t want to burden the Compositing Engine with one more chip – it is already complex. So, you can’t connect your CrossFire to a TV-set with an RCA or S-Video input; you have to use an external coder if necessary. This is one more drawback of the current version of CrossFire technology.

The cooler on the card doesn’t differ from the one that first appeared on RADEON X850 series cards. It is the same turbine that sucks air from inside the system case and drives it through the copper heat-spreader that contacts with the GPU die and then exhausts the hot air to the outside. The solution is efficient, yet rather noisy. The plastic casing of the turbine works as a resonator, so the cooler remains quiet only at the lowest speed of the fan. There’s a wide gap between the heat-spreader’s sole and the case of the Xilinx matrix. This gap is filled with strange white foam-like thermal paste. Its efficiency as of a thermal interface is doubtful considering the thickness of the layer of the paste (about 1 millimeter). But maybe this is enough to cool the heart of the Compositing Engine.

This is where the difference between the RADEON X850 XT and the RADEON X850 XT CrossFire Edition ends. The right part of the PCB copies the design of the RADEON X850 XT to a smallest detail. We’ve got an R480 processor here with ordinary 1.6ns GDDR3 memory from Samsung. The clock rates of the two versions of RADEON X850 XT coincide and are 520MHz for the graphics core and 540 (1080) MHz for the memory chips.

 
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