Power Tools 1993 November - Disc 2/Power Tools Plus (Disc 2 of 2)(November 1993)(HP).iso/hotlines/wsyhl/wkscsi/script1.txt

Text File | 1993-01-06 | 9.7 KB | 184 lines

SCSI Cables and Terminators on the Series 400

CAUTION: SCSI cables and terminators for connecting external
peripherals to Series 400 workstations must be ordered separately.
Failure to order these parts as needed will result in delivery of
unusable systems to your customers.

With the HP/Apollo merger, and the introduction of the Series 400, the
task of correctly configuring a SCSI system has become more complex.
Cabling and terminator issues continue to be a major source of
confusion. In order to help you, and to prevent shipping incomplete
systems to your customers, this guide summarizes all of the current and
available SCSI information.

Workstation Group Marketing is taking several additional steps to make
sure that SCSI hardware is ordered when needed. All future Series 400
price guides will include notes indicating that the cables and
terminators may need to be ordered. The soon-to-be-printed Series 400
Configuration Guide will include full SCSI information. We will also be
changing the O.P. instructions on the CPL for the Series 400 and all
SCSI peripherals indicating that cables and/or terminator should be
ordered.

Today, we have three different types of SCSI connectors, depending on
the device. Older SCSI devices (SPUs and peripherals) designed for
Apollo customers use a low density connector attached with thumb
screws. HP's devices have traditionally used a similar connector,
except that it uses a bail lock instead of the screws. When the Series
400 was designed back panel space was minimal, so we had to use a third
type of connector. It is much smaller, hence called high density, and
attaches with a squeeze lock similar to the HP bail lock.

This assortment of connectors makes it impossible to predict at the
factory which connectors and terminators will be needed in a customer's
system. Each part is fairly costly, so it is just not practical for
every SPU or peripheral to include all the SCSI hardware that could be
needed. Instead, no SCSI cables are shipped with Series 400 SPUs or
SCSI peripherals. All workstation SPUs ship only with the terminator
used by the SPU itself. Any cables and the terminator needed when
external SCSI peripherals are used should be determined from the
matrices below. The parts should be ordered as separate product
numbers, preferably on the same order as the workstation itself.

Keep in mind that cables and terminators must be ordered only when
connecting physically separate SCSI devices. No cables or terminator
must be ordered if the only peripherals used are built into the SPU
package (as with disks etc. in the 400s). Also, some SCSI devices like
the C2212A/D and C2213A/D may have multiple SCSI peripherals built into
a single enclosure. All the internal cables to connect these internal
peripherals are already installed. The only cables that must be ordered
are to connect the C2212A/D or C2213A/D with other separate boxes. A
terminator must be ordered for the last box on the chain of separate
SCSI devices.

In the Drawing Gallery files MATRIX1.GAL and MATRIX2.GAL you'll see the
latest version of the SCSI device, cable, and terminator matrices.
Explanations of cabling and terminator requirements follow the
matrices. Please use these matrices for configuring systems.

A couple of examples might help clarify the use of the table and
matrix:

1) Your customer is ordering a 400s with two internal 660 MB disks,
plus a C2212A with another disk and a DDS drive. Looking at the device
table, the 400s uses a high density connector (and since its not yet
November 1 the connector uses a squeeze lock). The C2212A uses a low
density bail lock. The cable matrix says that when going from a high
density squeeze lock to a low density bail lock, either a K2285 or
K2286 should be ordered. The C2212A will need a terminator, which is
the K2291. See Drawing Gallery file CABLE1.GAL.

2) Another customer is ordering a 400t connected to a C2212D with a
disk, and then to a A-ADD-SFLP 5 1/4" floppy. Let's also assume it is
after November 1. The table says that the first cable will go from a
high density thumb screw connector to a low density bail lock. A second
cable is required to go from the C2212D's low density bail lock to a
low density thumb screw. This time the matrix says that the first cable
should be K2296 or K2297, and the second K2283 or K2284. The last
device must be terminated. That is the floppy, using a low density
thumb screw. The matrix tells you to order a K2290. See Drawing Gallery
file CABLE2.GAL.

Cables

Traditionally SCSI cables have been shipped with the SPU, assuming the
SPU included the SCSI interface. On the other hand, neither HP nor
Apollo shipped cables with SCSI peripherals. Now on the Series 400 SCSI
cables are no longer shipped with the SPU. Cables must be ordered from
DMK via Instant Apollo using the appropriate product number. Cables are
needed only if some external SCSI device will be used with the SPU.

As shown on the cable matrix, the choice of cable depends on the two
devices to be connected. The first device will be connected to the SPU,
so one connector of the cable will be the high density variety on the
Series 400. The other connector will be low density thumb screw if the
peripheral is a former Apollo product, or low density bail lock if from
DSS division (or if some other former HP product). If another SCSI
device is then attached, the cable must be one with a low density
connector on both ends, with the choice of connecting mechanism again
depending on the source of the peripheral. The matrix lists all
supported SCSI devices using each type of connector.

Choices of length are available for each cable variety. Keep in mind
that the SCSI definition (currently) limits the total length of SCSI
cables to 6 meters. This includes the length of cabling internal to
each device, which fortunately is usually small.

Yet another change to your choice of cables is coming November 1. The
current high density connectors on the Series 400 use a squeeze lock
connecting mechanism. Tests have shown that the weight of a cable can
bend the connection enough to break electrical contact or even bend
connector pins. Therefore the high density connectors are being revised
to use a thumb screw connecting mechanism.  These new cables will be on
the Instant Apollo price list (AND IN STOCK) on November 1. The current
high density connector on the back panel of the Series 409 SPU's
already has holes to accept the new screws, so no retrofit of shipped
SPUs will be necessary. Also, cables with the current connectors will
still be supported, but should not be ordered once the improved cables
are ready.

The new cable numbers will be:

K2294.  9 m, high density thumb screw on one end, low density thumb
        screw on the other

K2295   1.5 m, high density thumb screw on one end, low density thumb
        screw on the other

K2296   .9 m, high density thumb screw on one end, low density bail
        lock on the other

K2297   1.5 m, high density thumb screw on one end, low density bail
        lock on the other

Speaking of availability, by the time you receive this your problems
with SCSI cable availability should be over. All current cables will
begin to flow into DMK stock by mid-September!

Terminators

By definition, the last device on a SCSI bus must have a terminator.
This assures that all electrical signals on the bus stay within the
specifications.

If no external SCSI devices are attached to the SPU, the SPU itself is
the last device on the bus and must be terminated. The 400t and 425t
were designed with a built-in terminator, so a separate terminator is
not needed as long as no external device is connected. The 400s and
433s use a different design and do require a terminator on the SCSI
connector even if no internal or external devices are present. The high
density terminator (K2289) is shipped automatically with all 400s and
433s workstations. The only reason to order a K2289 is as a spare or
replacement.

If one or more external SCSI devices are connected to the SPU, the last
device must have an external terminator. All SCSI peripherals have two
SCSI connectors. One is used for connection to the preceding device,
the other connected to the next device in the daisy chain. The
terminator attaches to the open connector on the last device in the
chain. These terminators are not supplied with the peripheral, again
for cost reasons. The last external device to be on the bus must be
determined, and the appropriate terminator ordered by product number.

The terminator needed must be the same connector type as that last
device. As before, HP divisions like DSS, Bristol, Greeley etc. all use
the low density bail lock and so require the K2291 terminator. Former
Apollo peripherals use the low density thumb screw and need K2290.

As discussed in the section on SCSI cables, the high density connectors
are converting to thumb screw connections. This will not effect the
terminators. The current high density connectors use a squeeze lock,
and there is no need to convert them to thumb screw (the SPU's
connector adapts to either). Therefore the K2289 will remain the
terminator used on the 400s and 433s after November 1.

There have also been rumors of "passive" versus "active" terminators.
The low density bail lock terminator (K2291) is essentially the same as
the terminator shipped previously with the Series 300. However, older
Series 300 terminators were passive, and they have recently been
improved by making them active. Don't be concerned about this. Either
version works fine and are interchangeable.  In fact, orders for a
K2291 may get active or passive versions until stock is purged of the
older style terminators.