ATI Radeon X800 XT Mac Edition

The ATI Radeon X800 XT Mac Edition was a high-end graphics card released by ATI Technologies on January 5, 2005 as an optional GPU upgrade for early Power Mac G5 models with an AGP slot. It is based on a chipset developed by ATI (which was later acquired by AMD).

Description
The Radeon X800 XT Mac Edition is based on ATI's R423 XT performance graphics chip that was fabricated by TSMC on the 130 nm process. The GPU clock speed was 475 MHz, which could be boosted to 500 MHz. It contained 256 MB of GDDR3 video RAM. The card features a dual-link DVI port capable of driving a digital display at up to 2560 x 1600 pixels, such as the 30-inch Apple Cinema HD Display, and an ADC port capable of driving a display up to 1920 x 1200 pixels, such as the 23-inch Cinema HD Display. It required an AGP x8 slot and needed no additional power cables, though it can be modified to work on an AGP x4 slot with reduced bandwidth. Installing a ROM Xtender file from ATI will also reduce fan noise when it is idling after the startup process has completed.

The Radeon X800 XT Mac Edition is slightly slower than the PC version of the Radeon X800 XT, which was released in December 2004 with a base clock speed of 500 MHz, mainly to reduce its list price. It is not practical to flash the PC version of the card as the video ports are different and the Mac Edition ROM (128 KB) is twice as big as the PC version (64 KB). Attempting doing so will render all but VGA output inoperable. The Mac Edition was also one of the video cards used by Microsoft in the Alpha Xenon Development Kit during early development.

Support
The Radeon X800 XT Mac Edition supports Mac OS X 10.3.5 (Panther) and later, though the documentation recommends at least Mac OS X 10.3.6. Support is assumed to have ended with Mac OS X 10.5.8 (Leopard), the last version from Apple to support PowerPC-based systems.

Some owners of Power Macintosh G4s with a slower AGP x4 slot found that it is possible to tape over or cut pins 3 and 11 on the card to switch it down from AGP x8 to x4 mode. However, the card is known to run hot and may require an auxiliary power cable as it can draw more peak power than an AGP x4 slot can provide. This modification will also render the card unusable in a Power Mac G5 unless successfully reversed.

Articles

 * REVIEW: ATI Radeon X800 XT Mac Edition versus GeForce 6800 Ultra and Others by Rob-ART Morgan at Bare Feats (2005-01-05)