I noticed today, while converting some lossless files into AAC that iTunes encodes noticeably faster from the hard drive (in this case 7200 RPM Lacie from sig) than from cd. Though this seems quite intuitive to me, it got me thinking. Is the bottleneck the combo drive, the ATA bus, a little of both, or something else? If it's the drive, how do PowerMacs manage so much faster encode times (yes, I do know the drive is faster)? I'm sure these questions are incredibly stupid, but curiosity cannot wait.