Many readers were puzzled regarding the new iMacG5 and Tiger specs. Indeed, according to Apple Core Image requires at least a Radeon 9600 XT.
In fact a Radeon 9600 is perfectly compatible with Core Image. It is the same for the Radeon 9600 Mobility which is also absent in Apple's listing.
To ensure that your GPU is supported, you simply need to open System info and look for the Tab Monitor and GPU.