It will depend on the mode of the ide channel in your computer.
Dma mode (dma33) is bandwith 33MB/s
kb/s is 33MB*1024 = 33792kb/s
dma multiword 2 is bandwith 16,6MB/s
kb/s is 16,6MB*1024 = 33792kb/s 16998kb/s
so 56x is about 8400kb/s
in the ide modes mentioned over the device can cope with 56X
//Regards Soaplover