Communicator e3000 MPE/iX Release 7.0 Express 1 (Software Release C.70.01) (30216-90328)

Chapter 4 65
PCI-SCSI Device Adapter Cards
PCI-SCSI Device Adapter Cards on HP e3000 N-Class and A-Class Systems.
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.
NOTE 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
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
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)