# cat /proc/ide/ide0/hda/settings

with 2.4 kernel on my system says:

  name                    value           min             
max             mode
  ----                    -----           ---             
---             ----
  current_speed           68              0               70              rw

the current_speed mode value is (see 'man hdparm') ... "For multi- word 
DMA, the value used is the desired DMA mode number plus 32. for 
UltraDMA, the value is the desired UltraDMA mode number plus 64."  So my 
drive is using UltraDMA mode 4.

Not sure how that works with SerialATA... anyone have observations?