Another good couple of web sites I found on this are www.mp3ar.com - the MP3 Public Project - which interfaces a Microchip PIC to and IDE CD-ROM or HDD. Iknow it's a PIC, but there is some other information regarding the IDE/ATAPI spec which is quite useful. Another site is www.codepuppies.com which is a personal web site of one of the design engineers who worked on the MP3 Public Project. He was very helpful and also has a lot of good downloadable info. I think there may also be some info on the Paulmon web site www.pjrc.com. Hope this helps.