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Chapter 4 - SCSI Installation (XVME-956/412)
BIOS Location Address
The BIOS requires 16K bytes in memory. This may be mapped in six locations from C8000H through
DFFFFH. Define a location which does not conflict with other system devices.
Hardware Interrupt Enable
The hardware interrupts may be enabled or disabled. There is an incompatibility among the module's
BIOS, DOS 4.0.1, and some CPU's BIOS. This incompatibility causes the system to stop running
during a SCSI boot operation. However, this is not a problem when the SCSI drive is not the boot
device or when a DOS version other than 4.0.1 is being used. I n situations where DOS 4.0.1 has to be
used and the SCSI drive has to be the boot device, interrupts may be disabled and the system will boot
correctly.
BIOS Functionality
The BIOS will only support SCSI disk drives and will support a maximum of two drives. T h e BIOS
only recognizes target:LUN values of 0:0 and 1:0. I f there is one SCSI drive, assign its target number
to 0:0. I f there are two SCSI drives, assign their target numbers to 0:0 and 1:0. T h e BIOS will not
recognize any drives with target numbers 2:0 and higher.
If there are two standard drives, the BIOS will not connect any SCSI drives. However, i f there is one
standard drive, a maximum of one SCSI drive will be connected by the BIOS. I f there are no standard
drives, the BIOS will connect a maximum of two SCSI drives. Use the drivers to overcome these
limitations.
The BIOS will assign SCSI drives sequentially after the standard hard drive. That is, i f there is one
standard drive and a SCSI drive, the standard drive will be assigned to C: and the SCSI drive (0:0) will
be assigned to D:. I f there are no standard drives and one SCSI drive, the SCSI drive (0:0) will be
assigned to C:. I f there are no standard drives and two SCSI drives, the SCSI drive (0:0) will be
assigned to C: and the SCSI drive (1:0) will be assigned to D:.
BIOS Booting Contentions
When a SCSI drive is assigned to C: and there is no floppy diskette installed in A:, the BIOS will
attempt to boot from the SCSI drive 0:0 assigned to C:. I f there is a diskette in A:, the system BIOS
will attempt to boot from A:.
If a standard drive is assigned to C:, then the system BIOS will attempt to boot from the standard drive
and no attempt will be made to boot from the SCSI drive.
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