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The New RADEON: A Family Portrait

RADEON X1800 XT

We’ll start with the senior model, RADEON X1800 XT. This graphics card is much longer than the RADEON X850 and similar in size to the GeForce 7800 GTX.

Such a long PCB isn’t just a whim of the developers. The chip consisting of 320 million transistors and the memory working at 750 (1500) MHz frequency consume a lot of power call for appropriate power circuitry, which occupies the entire rear part of the RADEON X1800 XT. Unlike on the GeForce 7800 GTX, the power transistors are placed in a single vertical row and are covered with a narrow heatsink. The GeForce 6800 Ultra used a similar design, by the way. The power elements of the circuit are controlled with a multi-phase Volterra VT1103 controller (you can see it below the 6-pin additional power connector on the snapshot). The rest of the card’s surface is concealed by the massive dual-slot cooling system which we dismantled to get a better view:

Memory chips on ATI’s graphics cards used to be placed in the shape of the letter L, but this time the engineers had to use the same placement as NVIDIA came to employ since GeForce FX. This measure was necessary to ensure stable operation of the memory at frequencies above 1200MHz. But even this placement of the chips required an ingenious wiring between the GPU and memory. The developers met their goal, even though they made the PCB very complex.

The card carries eight GDDR3 chips marked as Samsung K4J52324QC-BJ12. According to the specification, these 512Mbit chips have an access time of 1.25 nanoseconds and work at 2.0V voltage. The chips are rated to work at 800 (1600) MHz frequency, but the card clocks them at 750 (1500) MHz. Eight 512Mbit chips yield a total of 512 megabytes of graphics memory – this is the most powerful model in the RADEON X1800 series.

The left part of the PCB is not particularly interesting. Besides the ordinary DVI-I and S-Video connectors, there is a Rage Theater chip here which is responsible for capturing video from external sources. This solution looks somewhat odd in combination with the Avivo, but for some reason ATI didn’t use their more progressive Rage Theater 200 chip, equipped with 12-bit ADCs, even in the new-generation graphics cards. Well, the Rage Theater anyway ensures nearly the same video capture quality as the Philips SAA7115HL chip NVIDIA uses in its GeForce 7800 GTX.

A little higher you can see an empty seat, probably intended for an additional TMDS transmitter (to connect to high-resolution TFT panels across a DVI interface). Higher still, there’s a connector that looks like an old VESA feature connector that you could see on almost all graphics cards in the past. We are not sure about its purpose – maybe CrossFire configurations will be united with a special cable through such connectors in the future? The reverse side of the PCB doesn’t have anything of interest. Besides numerous small elements, there is a metal back-plate which prevents the PCB from bending under the cooler’s weight.

You can see the effect of the new 0.09-micron tech process with your own eyes here. Although the ATI R520 includes more transistors than the NVIDIA G70 does, the die size of the new GPU is noticeably smaller and is comparable to that of the 0.13-micron R480.

The R520 chip on our sample of the card was manufactured on the 37-th week of 2005, i.e. around the middle of September. This is indirect evidence of the manufacturing problems with the new GPU – ATI seems to have begun the mass production of the final revision of the R520 quite recently. The chip has a metal frame that protects it against chipping. The GPU frequency is 625MHz on the XT version of the RADEON X1800.

The cooling system deployed on the RADEON X1800 XT is nothing else but a slightly modified cooler from the RADEON X850 XT which should be known to you from our earlier reviews. The central point of this cooler is a copper heatsink which directly contacts the GPU die through a thin layer of dark-gray thermal paste. The memory cools down by giving its heat out to the massive aluminum base of the cooler through elastic pads. Like on the RADEON X850 XT, a blower drives air through the heatsink ribbing and exhausts it to the outside.

This cooler differs from the RADEON X850’s one in having a bigger heatsink and a different shape of the base. The bottom part of the casing is painted white and is adorned with a picture of the ATI symbol – the girl called Ruby with a sword in hand. Unfortunately, we have some grave apprehensions about the acoustic characteristics of the cooler. If the blower works at a higher speed than on the RADEON X850 XT, the noise will hardly be acceptable, especially since the closed casing works as a resonator. But we’ll check this shortly in the appropriate section of the review.

 
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