When I wrote about the incompatibility of the new ?Learn to Play? feature present in GarageBand '09 with PowerPC Macs, I positioned myself to believe that it was much more about performance limitations on these machines than the fact that Apple is discontinuing it for good. support for PowerPC Macs – ok, it doesn't make a lot of sense if we put a Power Mac G5 on the move, but you will understand Steve Jobs, right? – since the time has not yet come for this to happen, in my opinion.
In fact, GarageBand is not the only application with features not supported on older Macs. Some of the new iPhoto ?09 slideshow themes are also limited to G5 or Intel machines, depending on the case. For all of them to be available for use, the machine must have a GPU with at least 64MB of memory.
Otherwise, the limitations may vary, depending on your machine's processor. If it is a G5, only the themesClassic, Ken Burns, Scrapbook and Sliding Panels will be available. If it is a G4, only the themesClassic and Ken Burns can be used. An Apple support article is available with more details on the subject.
Come and agree: these themes depend directly on the Mac's GPU to run. Judging by the fact that some of them have remarkably advanced effects, it is obvious that they would not run on any Mac with a G4 processor, since the graphics power of these machines is quite limited compared to the current ones.
With the GarageBand case, the same thing: ?Learn to Play? requires a Mac that supports high resolution videos. Generally, a Power Mac with a G4 1GHz processor and 512MB of memory would do the job, but very limited by the nature of the hardware, not by the fact that the machine has a PowerPC chip. The joke I made at the beginning of this article related to this: I thought it was an exaggeration to make good G5 Macs that are probably on the table for many of you incompatible with ?Learn to Play?, but, in the second order, this case is simply private, what a pity for me …