I have a PowerMac G5 which I have recently succeeded in getting running with a Mac OS X 10.4. I was in for two big surprises: Firstly, the computer runs very fast, even with heavier software like an older version of Photoshop. The second surprise was when I opened the Activity Monitor. It would appear that this computer is either dual-cored or dual-threaded.
Did Apple indeed make dual-core (or dual-thread) PowerMacs?