The introduction of higher display modes means a higher load on the Compositing Engine and the XC3S400 array may prove a bottleneck in the highest resolutions. We will check if it is really so by performing practical tests in real-life applications.

It is possible that the image-compositing logic will be moved right into the graphics processor in future versions of CrossFire, although it’s not profitable to release two versions of the same GPU for Master and Slave cards, considering that multi-GPU configurations account for but a small share of the desktop 3D graphics market. Integrating the Compositing Engine into every produced chip is hardly justifiable, either: the die will be even more complex and the chip yield will be lower with a negative effect on the cost as well as the market price of graphics cards on such GPUs. A more likely way of further development is creating and using a specialized chip instead of the all-purpose programmable array with its companion chips; this may even make the whole image-compositing system a little bit cheaper.

The final image is sent to the digital input of a TFT panel by a pair of Silicon Image SiI170B transmitters with a combined bandwidth of 330MHz. According to ATI Technologies, the maximum resolution available with the new-generation CrossFire is 2560x1600 at 60Hz refresh rate. It means the new graphics subsystem supports such exotic products as the 30” Apple Cinema HD Display for which 2560x1600 is the native resolution.

A three-channel 330MHz, 10-bit ADV7123 digital-to-analog converter from Analog Devices is still employed for connecting the card to monitors with an analog interface. As we have said above, popular display modes are all available, up to 2048x1536@75Hz. So the main drawback of the previous version of the Compositing Engine – its inability to work in display modes higher than 1600x1200@60Hz – has been successfully resolved in the new version.

Talking about drawbacks, the new graphics card lacks TV outputs. It does not support S-Video or RCA because there would have to be an additional TV encoder on the Master card right after the DAC and this would make the Compositing Engine, quite complex as it is, even more complicated. YPbPr output is probably supported by means of a special DVI-YPbPr converter we described in our All-In-Wonder X1800 XL review . As for HDMI, devices with this interface are fully supported because HDMI is actually a variation of DVI – you’ll just need an appropriate (even though not very cheap) cable.

The RADEON X1800 CrossFire Edition doesn’t otherwise differ from the ordinary RADEON X1800 XT which is used as the Slave card in a CrossFire configuration. It also has 512 megabytes of GDDR3 memory in eight Samsung K4J52324QC-BJ12 chips. The graphics processor is clocked at the standard core frequency of the RADEON X1800 XT, i.e. at 625MHz, so the performance shouldn’t be far lower than that of the ordinary card.

As for using the new graphics card together with a RADEON X1800 XL, this is really possible, despite the serious difference in the clock rates of the cards as well as the twice lower amount of graphics memory installed on the X1800 XL. In this case half the onboard graphics memory of the RADEON 1800 XT CrossFire Edition is going to be turned off by the driver, but its operating frequencies will remain intact and there may be situations when the Master is idle waiting for data from the slower Slave card. The efficiency of this configuration will be far from optimal, yet the owner of a RADEON X1800 XL has no other way to improve the graphical performance of his PC by means of CrossFire technology as yet. As far as we know, ATI Technologies doesn’t have a Master version of RADEON X1800 XL in its plans.

The cooling system of the card hasn’t changed since the announcement of ATI’s new generation of GPUs. It is efficient thanks to the high-quality heat-spreader and remains rather quiet even if you are working long in 3D. As earlier, a very thick dark-gray thermal paste, probably Shin-Etsu, serves as a thermal interface between the GPU die and the heat-spreader’s sole. The memory chips have contact with the heat-spreader through elastic rubber-like thermal pads, traditional for products from ATI Technologies.