From: Eric Smith <eric(a)brouhaha.com> In one sense your right and in another your making it look complex where it's not. For scsi I have to deal with the SCSI interface chip (really nasty if it's 5380!). For IDE I write/read to registers at addresses, al having specific function. there is some sense of sequence and if you want it to work you need to talk to the right one in the right order or garbage ensues. I liken it more to talking to an Z80 SIO raw than making the SIO do HDLC and at the end of that link getting something to happen. IDE is much simpler. I've done SCSI it's not! Already known. The difference between IDE and SCSI(any) is that from the CPU side if I want to write the cylinder address to IDE I address the correct register and write (assuming not LBA). For SCSI I first have to talk to the scsi chip and tell it what to say to the disk. The later already is a full layer of protocal from what you want to do. The point originally being that IDE is the simplest disk interface there is of the available sets and from doing a driver for z80 I can say its easier than floppy as the interface if buffered, not time critical reads or writes as the data flys by. Allison