It's not actually that slow.. using an old 210Mb 2.5" ide It gets about 500K->700K/sec.. if you just blindly stream to it (no filesystem) it gains another 500K..

RangerGuy,
33.3mb/sec isn't an old ide.. that's UDMA mode 2..
The only way you can talk to the HD on the dreamcast is in slave mode (pio), and the
cpu has to do it all, but as quzar pointed out.. drivers. even after you built it you need a filesystem, and some sort of hook or drivers in KOS.. etc..