ATAPI DELAY

3/7/98

ATAPI Delay -- The ATA Packet Interface is used to access CDROM devices over an AT Attachment (IDE) interface. An annoying delay can occur during boot with certain ATAPI device configurations. This delay occurs when an ATAPI device is present on an IDE controller and there is only one device on the controller. It does not occur when there are two devices on the controller, or no devices on the controller or when there is only one non-ATAPI device on the controller.

The delay comes about when an ATAPI driver interrogates an IDE channel and finds an ATAPI device. The driver must then interrogate both the master and slave channels to determine whether one or two ATAPI devices are present. The ATAPI spec calls for a 30 second time out on the requests. If there are two ATAPI devices or an ATAPI device and a non-ATAPI device (such as an IDE drive), the responses will come in a second or so and the system will continue. However when there is only a single ATAPI device on the controller, a full 30 second timeout will occur on the unused channel.

Possible cures for this problem include installing a properly configured IDE drive on the unused connector on the offending controller's cable. Changing the CMOS setup so that the drive is set to NONE rather than AUTO is another possibility.

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