You can copy on the fly with a lot of slower drives. It just depends on your software and its compatibility with your TEAC drive as well as your cd burner. Example...I can't copy on the fly on my setup because I have a DVD drive that is not recognized as a compatible drive with my Sony USB burner. However, it will do a test and see that it is fast enough, but there is some problem that won't allow this function to work so I have to copy my files to my harddrive before I can burn(less coasters this way anyhow).