System Configuration Background For Standard Mode; Preparation - Adaptec AHA-1740A Technical Reference Manual

adaptec
Connection of a single-ended board to a differential drive or vice versa may cause
permanent electrical damage to one or both devices.

System Configuration Background for Standard Mode

The DOS operating system and standard BIOS supports two hard disk drives; drive
C and drive D. If two standard hard disk drives are installed, they are the only hard
disk drives accessible from the operating system. If one standard hard disk drive is
installed, the AHA-1740A/1742A/1744 BIOS allows DOS to access the SCSI drive
with the Target:LUN address of 0:0 as the second of the two supported drives (drive
D). If no standard hard disk drives are installed, the AHA-1740A/1742A/1744 BIOS
allows DOS to access the SCSI drive with the address of 0:0 as the first of two sup-
ported drives (drive C) and the SCSI drive with the address of 1:0 as the second drive
(drive D).
System booting is performed from the floppy drive if a floppy diskette is installed. If
no floppy is installed, system booting is attempted from the drive chosen as drive C
through the above process, whether the drive is a standard hard disk or a SCSI hard
disk. The AHA-1740A/1742A/1744 BIOS fully supports the extended partitioning ca-
pabilities of DOS for up to two drives. Adaptec supplies a range of products based on
the Advanced SCSI Programming Interface (ASPI) architecture that allow the sup-
port of more than two physical or logical devices under DOS. Many other operating
systems, including SCO Xenix and Unix, also have this feature and will allow the ac-
cess of any number of attached SCSI devices. Refer to Chapter Eight, Device Drivers
for more details. Peripheral devices such as SCSI tape, DAT, CD-ROM and others re-
quire device driver software to be installed.
Standard hard disk refers to the disks attached to the system by a standard ISA non-
SCSI disk controller. These standard hard disks can be set to the installed or not in-
stalled state by the Setup program that is supplied with each host computer. The
Setup program allows the user to select the number of standard hard disks that are
recognized by the system regardless of whether they are physically installed.

Preparation

Few preparatory steps need to be taken to install the host adapter in the host com-
puter. The floppy controller enable/disable jumper on the AHA-1742A is the only con-
figuration jumper. If you already have a floppy controller in your EISA system,
disable the floppy controller on the AHA-1742A by removing the right-most jumper
on jumper block J6.
SCSI bus terminators must be installed in the correct SCSI devices and the correct
SCSI addresses must be assigned to each peripheral device. Each board is shipped
(default) with termination resistors installed. Unless connecting both internal and ex-
ternal peripherals to the same board, there is no need to remove the terminating re-
sistors from the AHA-1740A/1742A/1744.
3-2
WARNING
AHA-1740A/1742A/1744