by Jim Hawkins Commercial Systems Division
With the introduction of N-Class and A-Class Systems, new device
adapter cards are required for the support of SCSI peripherals.
These new cards also require new software and new SYSGEN configuration
values. The purpose of this article is to provide an external "System
Administrator" view of these changes in MPE/iX. The opening
section of the article describes the new device Adapter cards. A
small section on Card Performance and Device Connection limits is
then provided for reference. Finally the closing section of this
article is a review of SCSI Terminology (which you may want to read
first if all of this is new to you). Note: Installation of HP e3000
Device adapter cards is to be performed by licensed HP Hardware personal only.
All documents referred to in this article are available http://docs.hp.com.
The configuration of these cards and attached SCSI devices using SYSGEN
is covered in a separate article in this Communicator.
New Device Adapter Cards for N-Class and A-Class Systems
There are four new Device Adapter Cards available for the
N-Class Systems: A4800A, A5149A, A5150A and, A5159A. A-Class Systems
support two of these four cards: the A4800A and A5149A. Each of
these cards can be plugged into one of the system PCI Buses and
will present one or two SCSI Bus port(s) to the outside world.
In addition, the N-Class and A-Class Systems each have a "Core
I/O" card which includes modules that provide SCSI peripheral
support. These Core I/O SCSI Buses are implemented using the same chip
set(s) as the new Device Adapter cards and so can be treated as
an embedded version of these new cards.
A4800A - Single Port FWD SCSI-2 (PCI bus) Adapter Card. This
card plugs into a PCI Bus on the system and presents a single SCSI
bus to the outside world. This SCSI bus allows connections to High
Voltage Differential (HVD) SCSI peripherals only. Historically on
the HP e3000, HVD SCSI devices have been called "Fast/Wide" devices. This
bus must be terminated using an HVD terminator; typically this is
a High Density (HD) 68-pin HVD Terminator such as the C2905A.
(Special Note: This card is not auto-terminating; it requires an
additional physical terminator such as A4700-67098 (1252-6520) be
installed on the card for proper bus operation. This terminator
should be included with the card but can easily be lost if you are
not careful.) For details see "A4800A PCI Ultra SCSI Host
Bus Adapter Service and User Guide."
A5159A - Dual Port FWD SCSI-2 (PCI Bus) Adapter Card. (N-Class
Only) This card plugs into a PCI Bus on the system and presents
two (2) independent SCSI buses to the outside world. These SCSI
Buses allow connections to High Voltage Differential (HVD) SCSI peripherals
only. (Historically on the HP e3000, HVD SCSI devices have been
called "Fast/Wide" devices.) Each of these buses
must be terminated using an HVD terminator; typically
this is a High Density (HD) 68-pin HVD Terminator such as the C2905A.
For details see "HP A5159A Dual Port PCI to Differential
Ultra SCSI Host Bus Adapter Service and User Guide."
A5149A - Single Port Ultra 2 SCSI (PCI bus) Adapter Card.
This card plugs into a PCI Bus on the system and presents a single
SCSI Bus to the outside world. This SCSI Bus is capable of operating
in either LVD or SE Mode. This determination is made automatically by
the card based upon the devices and termination present on the Bus;
there is no software control for this feature. This bus must be
terminated. Depending upon the cables/connectors being used, this
would typically be either a High Density (HD) 68-pin LVD/SE terminator
such as C2364A or, for Very High Density (VHDCI) 68-pin LVD/SE cables,
a C2370A. For details see "HP A5149A PCI to Ultra2 SCSI
Host Bus Adapter Service and User Guide."
A5150 - Dual Port Ultra 2 SCSI (PCI bus) Adapter Card. (N-Class
Only) This card plugs into a PCI Bus on the system and presents
two (2) independent SCSI Buses to the outside world. These SCSI
Buses are capable of operating in either LVD or SE Mode. This determination
is made automatically by the card based upon the devices and termination present
on the Bus; there is no software control for this feature. Each
SCSI bus must be independently terminated.
Depending upon the cables/connectors being used this would typically
be either a High Density (HD) 68-pin LVD/SE terminator such as C2364A
or, for Very High Density (VHDCI) 68-pin LVD/SE cables, a C2370A.
For details see "HP A5150A Dual Channel PCI to Ultra2 SCSI
Host Bus Adapter Service and User Guide."
N-Class Core I/O Card. This card contains embedded versions
of both an A5159A (Dual Port) and an A5149A (Single Port). The
A5159A portion of the Core I/O card supports the two internal system
disk slots - neither of these SCSI Buses are exported to the outside (i.e.
there is no way to connect external peripherals to these buses).
The A5149A portion of the Core I/O card presents a single LVD/SE
bus for the connection of device(s) external to the system (VHDCI
68-pin LVD/SE connector).
A-Class Core I/O Card. This card contains embedded versions
of both the A5159A (Dual Port) and a A5150A (Dual Port). The system
uses one port from each card to support a single internal disk and
presents the other SCSI bus to allow the connection of external SCSI
peripherals. Path 0/0/1/0 (from the A5159A) is provided with a
VHDCI 68-pin LVD/SE connector. Path 0/0/2/0 (from the A5150A) is
provided with a special HD 50-pin SE connector; this connector only
supports an 8-bit data path so only "narrow" SCSI devices
such as the DDS-3 Tapes may be connected.
SCSI Card Performance Limits and Device Connection Limits
(Primary source "A5149A PCI to Ultra2 SCSI Host Bus
Adapter Service and User Guide")
Table 4-1 SCSI Bus Widths and Speeds
SCSI Classification
HP Card Id (signal type)
SCSI Bus Width (Bits)
Maximum Data Rate (MegaBytes/Sec)
SCSI-1
HP28642A (SE)
8
5
Fast SCSI
HP28696A (HVD)
8
10
Fast Wide SCSI
"
16
20
Ultra SCSI
A4800A, A5159A (HVD)
8
20
Wide Ultra SCSI
" "
16
40
Ultra2 SCSI
A5149A, A5150A (LVD/SE)
8
40
Wide Ultra2 SCSI
" "
16
80
The above "Maximum Data Rate" values are
maximums that these cards can achieve. Actual Maximum Data Transfer
Rates are dependent upon a number
of factors including the type of peripheral, the storage enclosures
that these peripherals are placed within and the cables used to
connect them. For example:
SCSI-1 Devices were only certified to operate on the HP e3000 at
SCSI-1 speeds. While it is possible that newer SE-SCSI disks are
capable of working at higher speeds they are not certified to
do so.
HP6000 Series Mass Storage products (a.k.a. "Cars" boxes) and High
Availability Storage enclosures (A3311A, A3312A, a.k.a. "Jamaica")
will not support transfers at higher than "Fast" speeds
(e.g. Ultra or Ultra2).
A5616A "SureStore E Disk System HVD10" uses HVD signaling and LVD
Disk modules but internal components are SE-SCSI based. Since SE-SCSI
signaling is not defined at "Ultra2" speeds (see Table 4-2) this
cabinet is limited to Ultra speeds.
The PCSCSI DAM software will, by default, limit the bus operating
speed based upon the detected bus type according to the following rules:
If there is one or more SCSI-1 devices on a bus then the card
will operate at "SCSI-1" speed.
Except where rule #1 applies the software will set the bus speed
to "Fast."
CAUTION: Overriding software defaults to operate devices at
faster than certified speeds can cause erratic system behavior,
hangs and even data corruption.
Table 4-2 SCSI Bus Length vs. Number of Devices by Bus Type
SCSI Classification
SE (Meters)
HVD (Meters)
LVD (Meters)
Maximum Allowed Devices (Note 2)
SCSI-1
6
25
12.5
8
Fast SCSI
3
25
12.5
8
Fast Wide SCSI
3
25
12.5
16
Ultra SCSI
1.5
25
12.5
8
Ultra SCSI
3
--
--
4
Wide Ultra SCSI
--
25
12.5
16
Wide Ultra SCSI
1.5
--
--
8
Wide Ultra SCSI
3
--
--
4
Ultra2 SCSI
Note 1
Note 1
12.5
8
Wide Ultra2 SCSI
Note 1
Note 1
12.5
16
CAUTION: Exceeding cable length maximums may cause erratic
system behavior, hangs and/or data corruption.
NOTE: Single-Ended and High-Voltage Differential protocols are not
supported/defined at Ultra2 Speeds.This limit is based upon SCSI bus electrical
and timing characteristics only. MPE/iX may further limit the number of devices
allowed per bus based upon performance characteristics. Please see the "N-Class
Supported Peripherals" Article in this Communicator for additional details.
SCSI Terminology Primer
The SCSI Standard documents both the physical and electrical
connection between devices. There are a large number of options
and terms used to define the type of SCSI bus or device that one
is using. Luckily, on the HP e3000 only a certain subset of these options
have been supported. The most important characteristic to understand
is the type of electrical signaling the device is capable of using.
A secondary consideration is the type of connectors a device uses,
which will influence your cabling options. We'll cover
both of these items below.
SCSI Electrical Signaling Types:
At this time there are three different electrical signaling
types: Single-Ended (SE), High Voltage Differential (HVD) and Low
Voltage Differential (LVD). The original set of SCSI devices available
on the HP e3000 are known as Single-Ended SCSI devices.
These devices were typically connected via a 50 pin cable with
8 data bits (1 byte) and use +5 Volt signals to communicate at a
peak rate of 5Mbytes per second. These devices are also referred
to as a SCSI-1, Single-Ended Narrow or simply SE-SCSI. Examples
of these devices include DDS Tapes like the HPC1530B or Disks such
as the ST34573N which are typically connected to the HP28642A Device
Adapter Card. On the N-Class and A-Class systems SE-SCSI devices
are supported via connection to A5149A and A5150A PCI-SCSI Device
Adapter Cards.
A second type of SCSI device was introduced in the MPE/iX
5.0 release and is typically referred to as "Fast/Wide
SCSI" or F/W SCSI. These devices are connected via a 68
pin cable with 16 data bits (2 bytes) and use a +-5 volt differential
signal to communicate at up to 20 Mbytes per second. The term "Fast-Wide
SCSI" is actually incomplete in defining the type of device
being used; a more proper term would be High Voltage Differential
SCSI (HVD) using Fast Wide signaling. Examples of these HVD devices
include the DLT7000 Tape drive, numerous "Fast-Wide" Disks
such as the HPC2490WD or ST39173WD, all of which are typically connected
to the HP28696A Fast/Wide SCSI Adapter Card. On the N-Class and
A-Class systems, HVD devices are supported via connection to A4800A
and A5159A PCI-SCSI Device Adapter Cards.
With the introduction of the N-Class and A-Class Systems,
there is a new type of SCSI device available known as Low Voltage
Differential (LVD) Devices. These devices are connected via a 68
pin cable with 16 data bits (2 bytes) and use a +-3.3 volt differential signal
to communicate at up to 80Mbytes per second. As of the time that
this article is written there are no fully LVD devices being supported
on the HP e3000. The SCSI standard states that all LVD devices
should have the capability of operating in SE-SCSI mode. Thus,
the LVD Device Adapters that HP supports have the capability to
support both Single-Ended and LVD devices. This means that it is
possible for older SE-SCSI devices to be used with an LVD Device
Adapter (though they will transfer data at the lower SE-SCSI rate).
On the N-Class and A-Class systems, LVD devices would be supported
via connection to A5149A and A5150A PCI-SCSI Device Adapter Cards.
Physical Connectors and Cables
With these different electrical characteristics, there are
also different physical connectors. At this time HP supports devices
that use four different types of physical connectors: Low Density
(LD) 50-Pin (example DDS-2 C1530B), High Density 50-Pin (HP28642A
Device Adapter Card), High Density (HD) 68-Pin (HP28696A Fast/Wide
SCSI Adapter Card) and Very High Density (VHDCI) 68-pin (A5149A,
Single Port Ultra 2 SCSI (PCI bus) Adapter Card). This means there
are a large number of cable types in varying lengths, some with different
connectors on each end (LD50 -> HD50 or HD50 -> HD68
or HD68 -> VHDCI68, etc.) When ordering cables pay particular
attention to the type of connectors present on each device you are
connecting.
The type of physical connector does not explicitly dictate
the type of electrical signals that can be used. For instance
SE, HVD and LVD signals can all be transmitted through a 68-pin
cable with High Density connectors, but NOT at the same time! Hooking
up SE devices to HVD devices (or vice versa) can actually damage
the devices; so be cautious. Just because you can physically connect
doesn't mean that you should. (The complexity of this
issue is one reason that we recommend that all peripheral installation
be done by HP Technicians.)
Chapter 4 PCI-SCSI Device Adapter Cards
SCSI Device Configuration Examples for N-Class and A-Class HP e3000 Systems