thanks to philippe anel, the now completely misnamed
sd63xxesb ahci driver has support for the amd sb600 in
ahci mode.

generally, legacy support is enough unless you
1. have more than four sata devices; or
2. need to mix and match pata and sata; or
3. need hot plugging; or
4. need the very-last word in performance.

let me know if you've any problems or dids/vids to add.

- erik