This Version of "El Capitan" is a special edition for Mac Pro 1.1 & 2.1 who not working with newer OSX after the "Lion" (OSX 10.7.5) !!!
Use all new Feature of OsX 10.11.1 and stay Tune with New Apps
Just Install the Disk and Start your Mac !!!
IMPORTANT
Updating your Graphics Card to any Mac Support 512MB or 1GB (if you have 256MB or 320MB)