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Ultra SCSI for desktop PCs and servers

The Adaptec AHA--2940Ultra and AHA-2940Ultra
Wide PCI-to-Fast SCSI host adapters provide a powerful
multitasking interface between your computer's
PCI bus and SCSI devices (disk drives,
CD-ROM drives, scanners, tape backups, removable
media drives, etc.).

Product Details

System Environment
For Desktop PCs and Servers

Data Transfer Rate
Up to 20MB/sec

External Connectors
50-pin High Density

Internal Connectors
50-pin Standard

Bus Type
32-bit PCI

System Requirements
IBM-compatible PC-486, Pentium, or above
Windows NT, Windows 95, Windows 3.1, or DOS 6.0, OS/2, UNIX or Netware Operating System
PCI expansion slot
SCSI peripheral

Supported Protocols
SCSI-1
SCSI-2
SCSI-3
UltraSCSI

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.

To change the SCSI ID on your hard disk and other SCSI
devices, refer to the device¡¯s documentation.

The host adapter supports the SCSI Configured
AutoMatically (SCAM) protocol, which assigns SCSI
IDs dynamically and resolves SCSI ID conflicts automatically
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.

Most SCSI devices currently in use, however, do not
support SCAM. The SCSI IDs on these devices must
be set manually.

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.

SCSI Terminators
To ensure reliable communication, the SCSI bus must
be properly terminated. Termination is controlled by
a set of electrical resistors, called terminators. Terminators
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 controlled
by software commands via the SCSISelecta
utility. The default setting is Automatic, which works
like this:

If the AHA-2940Ultra detects that a cable is connected
to either its internal or external SCSI connector,
then it enables its terminators (the
AHA-2940Ultra is at the end of the SCSI bus).

If the AHA-2940Ultra detects that a cable is connected
to both its internal and external SCSI connector,
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.

Terminating SCSI Devices
On most internal SCSI devices the termination
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.

Installing SCSI Devices (8-bit & 16-bit)

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.

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 connectors
to accommodate all of your devices.

When Fast SCSI devices are connected to the host
adapter, the total length of all cables (internal and external)
must not exceed 3 meters (9.8 ft.) to ensure
reliable operation. If no Fast SCSI devices are connected,
the total length of all cables must not exceed
6 meters (19.7 ft).

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; configure
the device SCSI ID and terminators (terminate
the last internal device attached to the cable).

2) Install the SCSI device in your computer.

3) Plug the connector at one end of the internal SCSI
cable into the host adapter¡¯s internal SCSI
connector.

Make sure the colored stripe on one side of the
cable is aligned with pin-1 of the host adapter¡¯s
connector.
Pin-1 of the connector is usually designated
by a small triangle (s), or a ¡°1¡± on the
connector.

4) Plug the remaining connectors on the cable into
the connectors on the backs of the devices.
Make sure the colored stripe on the cable is
aligned with pin-1 of the device¡¯s connector.

5) Connect a DC power cable (from your computer¡¯s
power supply) to the power connector on
the SCSI device.

Connecting External SCSI Devices

If you are connecting external SCSI devices to your
host adapter, you must obtain an external SCSI cable
for each external device you install.

1) Prepare each SCSI device for installation; configure
the SCSI ID and attach a terminating plug into
the last external device.

2) Plug the connector at one end of the external SCSI
cable into the host adapter¡¯s external SCSI
connector.

3) Plug the connector at the other end of the cable to
either one of the SCSI connectors on the external
SCSI device.

4) To connect other external SCSI devices, daisychain
each device to the previous device until all
external SCSI devices have been connected.

Troubleshooting Checklist
If you have a problem during installation, check
these items first:

Have you installed the host adapter into a PCI
Rev 2.0 compliant computer?

Are all SCSI devices powered?

Are all SCSI bus cables and power cables properly
connected? Is pin 1 oriented correctly?

Does the host adapter and all devices on the SCSI
bus have unique SCSI IDs?

Are all devices on the SCSI bus terminated
properly?

Does your system CMOS setup require you to
enable PCI bus parameters? If so, see your
computer¡¯s documentation. Check that IRQ
channel assignment, board, and BIOS settings
have been made.

Did you install your host adapter in a bus master
PCI slot? Refer to your computer¡¯s documentation
or try another slot.

 

Last Update: 03 March 2004