I/O Subsystem
R
Intel
®
855PM Chipset Platform Design Guide
187
9.1.4.2.
S5/G3 to S0 Boot Up Procedures for IDE Swap Bay
The procedures listed below summarize the steps that must be followed during power up of an IDE
swap bay drive.
1.
ICH4-M powers up, IDE interface is tri-stated, disk drive is not powered up. IDE drive is
recognized as being on a separate power plane and its reset is different from the ICH4-M.
2.
BIOS powers on the IDE drive. e.g. GPIO is used to switch on a FET on the board.
3.
Once the IDE drive and interface is powered up, the ICH4-M exits from tri-state mode and begins
to actively drive the interface.
4.
Once ready, the BIOS can de-assert the reset signal to the IDE drive. e.g. GPIO routed to the IDE
drive’s reset pin.
9.1.4.3.
Power Down Procedures for Mobile Swap Bay
The procedures listed below summarize the steps that must be followed in order to remove an IDE
device from the mobile swap bay.
1.
User indicates to the system that removal of IDE device from the mobile swap bay should begin.
Once the system recognizes that all outstanding IDE accesses have completed, the reset signal to
the swap device should be asserted.
2.
The IDE channel (primary or secondary) that the device resides on should then be set to drive low
mode rather than the default tri-state mode. This requires setting the IDE_CONFIG register
(B0:D31:F0 Offset 54h) bits [19:18] or [17:16] to ‘10’ (10b). This will cause all IDE outputs to
the IDE drive to drive low rather than the default tri-state (which is useful during boot up to
prevent any IDE drives from entering a test mode).
3.
The IORDY Sample Point Enable bit of the IDE_TIM register for the appropriate IDE device
should then be set to ‘0’ to disable IORDY sampling by the ICH4-M. This ensures that zeros will
always be returned if the OS attempts to access the IDE device being swapped.
4.
Power to the isolated power plane of the IDE device can then be removed and the system can
indicate to the user that the mobile swap bay can be removed and the IDE device replaced.
9.1.4.4.
Power Up Procedures After Device “Hot” Swap Completed
The procedures listed below summarize the steps that must be followed after a new IDE device has been
added to the mobile swap bay and the swap bay must be powered back up.
1.
Once the IDE swap bay is replaced into the system, the power plane to the device should be
enabled once again.
2.
The IORDY Sample Point Enable bit of the IDE_TIM register for the appropriate IDE device
should then be set to ‘1’ to enable IORDY sampling by the Intel 82801DBM ICH4-M. This
allows the OS to access the IDE device once again and waits for the assertion of IORDY in
response to an access request.
3.
Once the system IDE interface is configured for normal operation once again, the reset signal to
the swap device should be de-asserted to allow the drive to initialize.
