The X800 XT and X600 XT

X800 XT reference board

ATI’s X800 XT

As you probably know by now, ATI’s new flagship is the RADEON X800 XT Platinum Edition. The Platinum Edition is built for the enthusiast who wants uncompromising performance, and is willing to pay a king’s ransom to get it. One OEM however didn’t like the thermals on the Platinum Edition board for PCI Express, hence the need to create a slightly slower XT part that generated less heat, as this OEM is a significant chunk of ATI’s business. This is how the PCI Express-only X800 XT was born.

The X800 XT sports the same 16-pixel pipeline architecture as the X800 XT Platinum Edition, only its memory and graphics core are clocked more conservatively: 500MHz on the core, and 500MHz (1.0GHz effective) on the memory. Also like the PCI Express X800 XT Platinum Edution, the X800 XT requires an external power source to keep the card fed with juice while the PCI Express version of the X800 PRO doesn’t need an external power connection. A new 6-pin plug has replaced the Molex connector found on AGP boards (an adapter is provided just in case your power supply doesn’t have the new connector on it):

X800 XT ships with an adapter

Note the new connector for PCI Express

Physically the X800 XT looks just like previous X800 boards, ATI has made no changes to the reference design. The only distinctive characteristic that separates the X800 XT from previous AGP-based X800 cards we’ve benchmarked is its longer PCI Express interface, and while our board is equipped with video input support (which is provided by the Rage Theater chip on the underside of the board) final retail boards may or may not ship with this feature onboard.

PCI Express is longer than AGP

Our board shipped with 2.0ns GDDR3 memory modules (part number K4J55323QF), which is good for 500MHz exactly. Platinum Edition reference boards have been shipping with 1.6ns modules.

ATI’s OVERDRIVE software functions perfectly with the RADEON X800 XT, just as it does with the Platinum Edition. Unfortunately, the core clock frequency was limited to just 506MHz in our testing, an adjustment of just 6MHz over default (temperature reading was 45 degrees Celsius). Hopefully with a bit more prodding we can eventually get the X800 XT to run a little higher than this. We should also note that in order to compare the performance of the X800 XT to its AGP-equivalent, we underclocked an X800 XT Platinum Edition to the X800 XT’s standard clocks using Powerstrip.

X600 XT

If you recall our X600/X300 preview, you’ll remember that the X600 is essentially based off the RADEON 9600 XT architecture; that is the chip sports a four pixel pipeline configuration, with one texture unit per pixel pipeline. Unlike its “X” designation suggests, the X600 family doesn’t support one of the X800’s key new features, 3Dc.

The X600 XT

Back of the card

ATI has made one enhancement to the X600 XT in particular though, the memory clock frequency has been cranked up. With its 500MHz core, often times the RADEON 9600 XT was craving more memory bandwidth. By bumping the memory clock speed up to 370MHz (740MHz effective), memory bandwidth shouldn’t be as much of an issue, especially at high resolutions or when AA/AF is applied. ATI even provides some headroom for overclocking by using 2.5ns Hynix memory modules (part number HY5DU283222AF-25). These modules are rated for up to 400MHz (800MHz effective).

Physically, the X600 XT reference board more closely resembles the RADEON 9600 PRO more than the RADEON 9600 XT. Fundamentally all three cards are based on the same 0.13-micron core with copper interconnects and low-k dielectric material, so this shouldn’t come as too much of a surprise, but we still would have liked to have seen ATI transfer the RADEON 9600 XT’s larger, more powerful heatsink/fan unit onto the X600 XT as well.

Hopefully ATI will get the red PCB and beefier heatsink on retail X600 XT cards

The X600 XT doesn’t support OVERDRIVE in the current CATALYST driver.

Overclocking

We tried to use both the latest version of Powerstrip (3.49) and Powerstrip’s latest beta to overclock our PCI Express ATI cards, but unfortunately, neither Powerstrip version correctly detected the clocks on our PCI Express cards. Therefore, we decided to omit overclocked testing until we’ve got a software utility that properly detects both boards.