Any of the PPC platforms couldn't mine coins worth a crap. Even a top end PPC Mac mining coins doesn't come close to even a low end GPU - I have tried it, and there wasn't even a break even factor to it, really. My 5 year old nVidia GPU's had better throughput, and nVidia GPU's are notoriously poor for mining, even the modern high end Titan's like I have in this machine don't come close to modern mid-range AMD cards.
There's mining clients for the PPC Mac platform, give them a whirl. Not a fault of the platform, CPU's just do not mine efficiently, and even mutli GPU PC's have a hard time turning a profit on BTC. Bitcoin is now in the ASIC age, profits wise.