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Inside Macintosh: Operating System Utilities /

Chapter 9 - Start Manager / Start Manager Reference

Routines / Identifying and Setting the Default Startup Device

SetDefaultStartup

You can use the SetDefaultStartup procedure to write information to parameter RAM that specifies the default startup device.

PROCEDURE SetDefaultStartup (paramBlock: DefStartPtr);

paramBlock

A pointer to a default startup device parameter block.

for a slot device

-->	sdExtDevID	SignedByte	External device ID.
-->	sdPartition	SignedByte	Reserved.
-->	sdSlotNum	SignedByte	Physical slot number.
-->	sdSRsrcID	SignedByte	Slot resource ID (SResourceID).

for a SCSI device

-->	sdReserved1	SignedByte	Reserved.
-->	sdReserved2	SignedByte	Reserved.
-->	sdRefNum	Integer	Driver reference number.

DESCRIPTION

The SetDefaultStartup procedure writes information to parameter RAM that specifies the default startup device. The default startup parameter block of data type DefStartType defines two kinds of startup devices: either a slot or a SCSI device. To specify a slot device as the default, pass the external device ID, the slot number, and the slot resource ID. The external device ID, supplied by the slot's driver, identifies a particular device connected through that slot. It's possible that the card in this slot could have several devices connected to it.

To specify a SCSI device as the default, pass its driver reference number (always negative) in the sdRefNum field. To specify no device as the default, pass a value of 0 in this field.

ASSEMBLY LANGUAGE INFORMATION

The registers on entry and exit for this routine are

Registers on entry
A0	Address of the default startup device parameter block

Registers on exit
A0	Address of the default startup device parameter block

SEE ALSO

For more information about the default startup device parameter block see "The Default Startup Device Parameter Block" beginning on page 9-18.

To retrieve information about the default startup device, see the description of the GetDefaultStartup procedure described on page 9-20.