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Introduction
1
Introduction
The Adaptec AHA
®
-2940Ultra and AHA-2940Ultra
Wide PCI-to-Fast SCSI host adapters provide a pow-
erful multitasking interface between your com-
puters PCI bus and SCSI devices (disk drives,
CD-ROM drives, scanners, tape backups, removable
media drives, etc.). Collectively, both host adapters
are referred to as the AHA-2940Ultra/2940Ultra
Wide. The following figures show the major compo-
nents on the AHA-2940Ultra and AHA-2940Ultra
Wide.
1
Adaptec AHA-2940
Ultra
50-pin 8-bit Internal
SCSI Connector
Host
Adapter
LED
AIC-78xx SCSI Protocol Chip
50-pin 8-bit
External
SCSI
Connector
Host Adapter
BIOS
LED Connector
Adaptec AHA-2940
Ultra Wide
50-pin 8-bit Internal
SCSI Connector
Host
Adapter
LED
AIC-78xx SCSI Protocol Chip
68-pin 16-bit
External
SCSI
Connector
LED Connector
Host Adapter
BIOS
68-pin 16-bit
Internal SCSI
Connector 2
Installing the Host Adapter
Follow these instructions to install the host adapter:
1
Turn
OFF
power to the computer and peripheral
devices and disconnect the power cords.
2
Remove the cover from the computer case.
3
Locate an unused 32-bit PCI expansion slot (the
slot must support Bus Master data transfers);
unscrew and remove the metal bracket that covers
the card-slot opening. (Save the screw to use when
securing the host adapter in your computer.)
PCI slots are shorter than ISA or EISA slots and
are typically white. One of these may be a shared
slot into which you can insert either an ISA/EISA
board or a PCI board.
4
Insert the host adapter in the PCI expansion slot.
Press it down firmly so that the contacts are
securely seated in the slot.
5
When the host adapter is firmly seated in the
expansion slot, secure the metal bracket of the host
adapter with the screw you removed in step 3.
Do not replace the computer cover or reconnect your
computer and peripherals to their power sources yet!
SCSI Configuration Guidelines
Before installing your SCSI devices, you should
understand the basic SCSI concepts described in this
section. The information will help you set up your
host adapter and devices so they function properly.
SCSI ID Numbers
Each device attached to the host adapter, as well as
the host adapter itself, must have a unique SCSI ID
number (0 to 7 for the AHA-2940Ultra, and 0 to 15 for
the AHA-2940Ultra Wide).
We recommend that you leave the host adapter set
to its default setting of SCSI ID 7. If you need to
change the host adapter SCSI ID, see Configuring the
Host Adapter on page 7. To change the SCSI ID on
2
3 3
your hard disk and other SCSI devices, refer to the
devices documentation.
The host adapter supports the SCSI Configured
AutoMatically (SCAM) protocol, which assigns SCSI
IDs dynamically and resolves SCSI ID conflicts auto-
matically at bootup. If your system includes SCSI
disk drives or other devices that support SCAM, you
do not need to manually assign SCSI IDs to these
devices. To enable SCAM support, see Configuring
the Host Adapter on page 7.
Most SCSI devices currently in use, however, do not
support SCAM. The SCSI IDs on these devices must
be set manually. To change the SCSI IDs on these
devices, refer to the devices documentation.
Note:
If you plan to boot your computer
from a SCSI device attached to the host
adapter, set the Boot Target ID setting in the
SCSISelect utility to correspond to the SCSI
ID of the device you are booting from (see
Configuring the Host Adapter on page 7).
SCSI Terminators
To ensure reliable communication, the SCSI bus must
be properly terminated. Termination is controlled by
a set of electrical resistors, called terminators. Termi-
nators must be placed (or enabled) at the two
extreme ends of the SCSI bus. All devices that lie
between the ends must have their terminators
removed (or disabled).
Terminating the AHA-2940
Ultra
Termination on the AHA-2940Ultra itself is con-
trolled by software commands via the SCSISelect
®

utility. The default setting is Automatic, which works
like this:
s
If the AHA-2940Ultra detects that a cable is con-
nected to either its internal or external SCSI con-
nector, then it enables its terminators (the
AHA-2940Ultra is at the end of the SCSI bus). 4
s
If the AHA-2940Ultra detects that a cable is con-
nected to both its internal and external SCSI con-
nector, then it disables its terminators (the
AHA-2940Ultra lies between the ends of the SCSI
bus).
We recommend that you leave the AHA-2940Ultra
set to its default setting of Automatic. If you want to
manually enable or disable the AHA-2940Ultra ter-
mination setting, see Configuring the Host Adapter on
page 7.
Terminating the AHA-2940
Ultra
Wide
Termination on the AHA-2940Ultra Wide itself is
controlled by software commands via the SCSISelect
utility. The default setting is set to Automatic.
We recommend that you leave the AHA-2940Ultra
Wide set to its default setting of Automatic. If you
want to manually set the AHA-2940Ultra Wide ter-
mination setting, see Configuring the Host Adapter on
page 7. The following table lists the termination set-
tings for manual configuration.
Terminating SCSI Devices
Read the devices documentation to determine how
to enable or disable termination on your particular
SCSI device(s). On most internal SCSI devices the ter-
mination setting is controlled by a jumper or a
switch. On other internal SCSI devices you must
physically remove or install resistor module(s). On
most external SCSI devices, a terminating plug (a
resistor pack embedded in a small plug) is installed
or removed to control termination.
AHA-2940
Ultra
Wide Termination
Devices Connected to AHA-2940
Ultra Wide
Low
High
68-pin internal connector only
ON
ON
68-pin external connector only
ON
ON
68-pin internal and 68-pin external connectors
OFF
OFF
50-pin internal connector only
ON
ON
50-pin and 68-pin internal connectors
OFF
ON
50-pin internal and 68-pin external connectors
OFF
ON 5
Installing SCSI Devices
You can connect up to a total of seven internal and
external 8-bit SCSI devices to the AHA-2940Ultra, and
up to 15 devices (seven 8-bit internal and eight Wide
(16-bit) internal or external SCSI devices, or 15 Wide
internal and external SCSI devices) to the
AHA-2940Ultra Wide.
Note:
You may only use two of the
three connectors at any one time on the
AHA-2940Ultra Wide host adapter.
Choosing SCSI Cables
The cables required to connect SCSI devices are
determined by the type of devices you are installing,
as described in the following table.
If you purchased your AHA-2940Ultra/2940Ultra
Wide in an Adaptec kit, the kit includes an internal
SCSI cable that allows you to connect up to two
internal SCSI devices (the AHA-2940Ultra kit
includes a 50-pin internal SCSI cable, and the
AHA-2940Ultra Wide kit includes both a 50-pin and
a 68-pin internal SCSI cable). If you are connecting
more than two internal SCSI devices, you must
obtain an internal SCSI cable with enough connec-
tors to accommodate all of your devices.
Adaptec sells high-quality internal and external SCSI
cables. If your reseller does not stock these cables,
you can order them directly from Adaptec.
When Fast SCSI devices are connected to the host
adapter, the total length of all cables (internal and
SCSI Device Type
AHA-2940
Ultra
AHA-2940
Ultra Wide
8-bit Internal SCSI
50-pin internal
SCSI cable
50-pin internal
SCSI cable
8-bit External SCSI
50-pin high-density
external SCSI cable 16-bit Internal
Wide SCSI 68-pin internal
SCSI cable
16-bit External
Wide SCSI 68-pin external
SCSI cable
4 6
external) must not exceed 3 meters (9.8 ft.) to ensure
reliable operation. If no Fast SCSI devices are con-
nected, the total length of all cables must not exceed
6 meters (19.7 ft). See your devices documentation
to determine if it is a Fast SCSI device.
Connecting Internal SCSI Devices
If you are connecting internal SCSI devices, make
sure you have an internal SCSI cable with enough
connectors to accommodate all of your devices.
1
Prepare each SCSI device for installation; config-
ure the device SCSI ID and terminators (terminate
the last internal device attached to the cable). For
instructions, see the devices documentation as
well as SCSI Configuration Guidelines on page 2.
2
Install the SCSI device in your computer. Refer to
your computer and device documentation for
instructions.
3
Plug the connector at one end of the internal SCSI
cable into the host adapters internal