Staggered spinup is sometimes implemented via pin #11 in the SATA power connector. This same pin is also used to drive an activity indicator.
http://pinouts.ru/Power/sata-power_pinout.shtml
Most desktop implementations will permanently ground pin #11 in the PSU cable, in which case you will have no spinup control via this route. An enterprise server, OTOH, may provide control over pin #11 via electronics in the backplane.
If your RAID card or motherboard chipset offers staggered spinup, then I suspect it will be implemented via PUIS, not via SATA pin #11.
