Q19: Hard disk does not spin up - PUIS (Power Up In Standby).
A19: The optional Power-Up In Standby (PUIS) feature set allows devices to be powered-up into the Standby power management state to minimize current at power-up and to allow the host to sequence the spin-up of devices.
This optional feature set may be enabled or disabled via the SET FEATURES command or may be enabled by use of a jumper, or both. When enabled by a jumper, this feature set shall not be disabled via the SET FEATURES command.

Once this feature is enabled in a device, the device shall not disable the feature as a result of processing a power-on reset, a hardware reset, or a software reset.

If the device implements this SET FEATURES subcommand and power-up into Standby is enabled, the device shall remain in Standby until the SET FEATURES subcommand is received.

If the device does not implement the SET FEATURES subcommand to spin-up the device after power-up and PUIS is enabled, the device shall spin-up upon receipt of the first command that requires the device to access the media, except the IDENTIFY DEVICE command or the IDENTIFY PACKET DEVICE command.

Solution for HDAT2 program: if you have a hard disk with enabled PUIS (cannot spin up and BIOS cannot recognize this drive) run program with parameter /W Wake/Spin-up the drive:

HDAT2 /W

Without the parameter /W, when PUIS is detected on the disk, the program asks you to turn off PUIS.

List of parameters: HDAT2 /? or HDAT2 /h.