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Chapter 4 - SCSI INSTALLATION
4.1 I N T R O D U C T I O N
This chapter describes how to install the SCSI Device Controller Module. T h e SCSI Module provides
two software interfaces: the drivers and the BIOS. The drivers are files loaded by the CONFIG.SYS
file as devices. They reside in system RAM. The BIOS is an extended BIOS which resides as an 8-bit
entity on the AT bus. Either the BIOS or the drivers may be used for system booting. The user must
decide which is appropriate for the given application.
WARNING
All Xycom XVME-PC/AT CPU modules with functional revision levels of
4.1 or higher require the XVME-956/412. Use of the XVME-956/402 on
a PC/AT CPU with a functional revision of 4.1 or higher, will cause damage
to both modules. Likewise, the use of the XVME-956/412 on a PC/AT
CPU module with a functional revision less than 4.1 will also damage both
modules.
The following are mutually exclusive options to be considered in deciding to use BIOS or the drivers:
• O n l y the BIOS supports booting from the SCSI interface. The drivers cannot be used in these
applications
• T h e drivers' location in system RAM provides faster SCSI interactions
• T h e BIOS may only be used in systems with one or no standard hard drives. There must be
no more than two drives, (standard and SCSI), in the system. T h e
drivers
support up to 56
devices and must be used when more than two are needed.
• T h e BIOS is configured via switches on the module which is typically embedded in the
system. T h e drivers are configured via parameters in the CONFIG.SYS file.
• T h e BIOS only recognizes SCSI targets 0:0 and 1:0. The drivers must be used to access
other targets.
• T h e BIOS only works with drives. The drivers must be used to access other types of SCSI
devices.
• T h e drivers support multi-tasking. The BIOS does not.
• Removable media hard disks should
only
be installed under the drivers. I f installed under the
BIOS,
do not change media
or unpredictable results may occur or data may be lost.
4-1