The update is applicable for those Mac Pros that include one or more ATI Radeon HD 2600 XT graphics cards installed. It's designed for use with Mac OS X v10.5.2 with the Leopard Graphics Update installed.
The update 'improves system stability,' according to Apple. No additional details were available as Macworld posted this article.
This story, "Apple Updates Radeon HD 2600 XT Firmware" was originally published by Macworld.