Digital PDFs

EK-KDA5Q-UG-001

November 1984

40 pages

Original

1.7MB

view download

OCR Version

1.5MB

view download

Document:	KDA50-Q User Guide
Order Number:	EK-KDA5Q-UG
Revision:	001
Pages:	40
Original Filename:

OCR Text

EK-KDA5Q-UG-001

KDA50-Q
USER GUIDE

(SEMI-FINAL REVIEW)

Digital Equipment Corporation
Colorado

Springs,

Colorado

lst

Edition,

November

1984

The material in this manual is for informational purposes and
is
subject
to change without notice.
Digital Equipment Corporation
assumes no responsibility for any errors which may appear in this
manual.
Digital
Equipment
Corporation makes no representation
that the
interconnection
of
its
mass
storage
products
with
products
of other manufacturers will not infringe on existing or
future patent rights.
Nor do the descriptions
contained
herein
imply
the
granting
of licenses to make, use, or
gell equipment

constructed or configured in accordance herewith.t?‘The Digital
Storage

Architecture

(DSA)

and Standard Disk

mass
storage
products
manufactured
Corporation
are designed to work with

by
host

Interconnect

Digital
computers

(SDI)

Equipment
and DSA and

SDI products designed by Digital Equipment Corporation,
Digital
Equipment Corporation
assumes no responsibility or liability if
the host computers, controllers, mass storage servers,
tape,
or
disk products of another manufacturer are used with these DSA and
SDI

products.

Printed

in U.S.A.

This equipment generates, uses,
and
may
emit
radio
frequency
energy.
This equipment has been type tested and found to comply
with the limits for
a
Class
A
computing
device
pursuant
to
Subpart
J of Part 15 of FCC Rules, which are designed to provide
reasonable protection against such radio
frequency
interference
when
operated
in
a
commercial environment.
Operation of this
equipment in a residential area may cause interference
in
which
case the user at his own expense may be required to take measures
to correct the interference.

The following are trademarks of
Maynard,

Digital

Equipment

Massachusetts:

DEC

DECnet

DECUS

DECsystem-10
DECSYSTEM-20
DECwriter

0s/8

RSTS

DIGITAL

Digital

Logo

OMNIBUS
PDT

KDA50-Q

PDP

DIBOL

UNIBUS

Edusystem

RSX

VAX

MASSBUS

VMS

RAS81

RA60
RAS80

HSC50

UDAS0
IAS

Corporation,

CONTENTS

o
o

o«
o

¢
o

2.3.2
2.3.3
2.4

. ¢« ¢ ¢
Internal SDI Cables
. « ¢ ¢
External SDI Cables
ALTERNATE INSTALLATION PACKAGE

¢
¢
«

¢
o
¢

o
o
o

o
o
¢

o
o
o

2.5

FIELD ACCEPTANCE TEST PROCEDURE

2.4.1
2.4.2
2.4.3
2.5.1
2.5.2
2.5.2.1
2.5.2.2
2.6

2.6.1

e b

et b

o
o
s
4

T
[ IR T

o
5
o

[

¢«

[]
[)

I/0 Bulkhead Installation

Mounting The Alternate Bulkhead Assembly
. . . .
Internal SDI Cable Installation
. . . .
External SDI Cable Installation
.

Drive-Resident Diagnostics . . ¢
. .« o ¢ o
Subsystem Diagnostics
PDP-11 Subsystem Diagnostics .
. .
VAX Subsystem Diagnostics

SYSTEM AND SOFTWARE CONSIDERATIONS

System Clock Or Timer

«
o+
.
«
.

¢
o
.
.

o
o
.
.

&
&

.
.

N P

[]
®
[]
[]

o
o
s
o
e

[]
[

[]

2.3.1

&«

yoeuo
— O O 0 0>

«
o

]

¢«
e

Cable Installation .

WNe

Final M7165 Installation . «
STANDARD INSTALLATION PACKAGE

M7165 Intermodule

2.2.7
2.3

2.2.6

.«

INSErtion

¢«

M7164 Module Installation

2.2.5

M7165 SDI Cable Installation And Initial

2.2.4

2.2.3

[]

M7164 Intermodule Cable Installation .

[]

.
.

.
.
o
o
.

&«

INTRODUCTION

INSTALLATION

.
MODULE PREPARATION AND INSTALLATION
2.2
Jumper
And
I/0 Page Address Switches
2.2.1
o o o« o o o o o o o o o
OBUS TuiNg
2.2.2
. « ¢ ¢« o o
QBUS Device Positions
2.2.2.1
. . .
Parameter
KDA50-Q Burst Rate
2.2.2.2

2.1

o
o

b e bt et et e e

o
o

¢
o

o
o

o«
o

o
«

o«
o«

RELATED DOCUMENTATION

[]
[]
[]

.«
.

Hardware Services
Software Services

[]

DIGITAL CUSTOMER SERVICE CONTRACT OPTIONS

o
o
o
@
o
o

o
o
o
o
o
o

[]

o
¢
o
o
o
o

o
o
o
o
o
e

[]

¢
o
o

¢
¢
e
¢
o
o

o
o«

The SDI Module . ¢« ¢ ¢ o ¢
The Processor Module . . «
KDA50-0Q FUNCTIONAL MICROCODE
. . «
OBUS Control Stream
« «
.
Stream
Drive Control
o o
e
TIONS
KDAS50-Q SPECIFICA

o
o
o
o
o
o

[]

[}

[]

]

KDA50-Q MODULES

oooooooooooooooooolv—‘OOQOQOQ

MASS STORAGE CONTROL PROTOCOL

WoJddooummbdecWwWwwivNn
-

CHAPTER 2

[]

1.8

[]

1.7.1
1.7.2

DIGITAL STORAGE ARCHITECTURE (DSA)

1.7

1.5
1.5.1
1.5.2
1.6

[

1.4.1
1.4.2

1.4

[]

1.3

1.2

&«

DISK CONTROLLER

[)

1.1

INTRODUCTION

[

CHAPTER 1

2.6.2

EXrror

2.6.3
2.6.4

Drive Numbering
. .« ¢«
S5ystem Performance And

CHAPTER 3

KDA50-Q

LOGS

=«

PROGRAMMER

2=27

¢« ¢ ¢ ¢
¢
Operation

¢
.

o
.

o«
.

o
.

2-28
2-28

INFORMATION

«.

INFORMATION

3.1

KDA50-Q-SPECIFIC

1-1

KDA50-Q

Disk

2-1

KDAS0-Q

Tllustrated

PROGRAMMING

3-1

*IGURES

Subsystem Configuration

1-1

o
o

2=2

2-2
2-3

M7164 QBUS Address switch and Jumper Locations .
KDA50-Q Switch Setting for Address 172150 (F468

2-6

2-4

HeX) o e . . e o
Address Selector

.
o
o

2"'6
2=7
2=7
2-11
2-12
2-14
2-14
2-15
2-15
2-16

Parts

2-12
2-13

. °
. .
M7165 Jumper Locations .« « «
o o ¢ o o«
KDA50-Q Intermodule Flat Ribbon Cables
M7165 SDI Cable Assembly Installation
BAll 2x3 Adapter Plate Installation
.
Bulkhead to I/O Panel Attachment . . .
Internal SDI Cable Installation
. .
Grounding Internal SDI Cable(s)
[TBD]
External SDI Cable Installation [TBD]

.
«
o
.
.
.
¢«
e
e
.

.
&«
o
.
.
.
¢«
o
o«
.

.
¢
o
.
.
.
¢«
o
o
.

.
&«
o
.
.
.
«
o
o
.

.
o
o
.
.
.
«
o
o
«

Alternate

¢«

2-18

2-14

Diagnostic

2-21

1-1

KDA50-Q

2-1
2-2

KDA50-Q Assemblies . . .
LED Error and Symptom Codes

2-5
2-6
2-7
2-8
2-9
2-10

2-11

. . . ' ' . ° . .
Switch Operation

Bulkhead

Assembly

LED Locations

¢«

KDA50-Q

¢«

Modules

TABLES

Specifications

¢«

1-6

e
c

o
e

o
o

o
s

o
e

o
o

2=1
2=21

CHAPTER 1
INTRODUCTION

NOTE

Information

that

1is

currently

unavailable

designated by: [TBD].

1.1

DISK

CONTROLLER

The

KDA50-Q

intelligent

RA series disk

controller which

Two gquad-height modules, the
Standard
Disk
Interconnect
module and the Processor module, make up the KDA50-Q.

radial

bus

configuration

that

operates

QBUS.
(SDI)

to any CPU

16-bit,

The KDA50-Q uses

drives

interfaces

four,

instead

on a

the

conventional
daisy-chain
(serial) method.
Radial configuration
means that there is a separate
1/0
cable
going
to
each
disk
drive.
Figure 1-1 shows the KDA50-Q subsystem configuration.

cpu cadinel
HOST CPU

/”—“fi‘
Ly

Il 1
M11bS

J—

EXTEARAL

SOI CABLES
UP TO FOUR

SOt DISX ORIVES

INTERNAL /

SO! CABLES

\ CONNECTOR
BSWLKHEAD

Fisueo 1= Kb o= disk _faé‘)"%’fi‘?:’.m Cor - sufat

INTRODUCTION

1.2

DIGITAL STORAGE ARCHITECTURE

(DSA)

The KDAS50-Q belongs to the family of DSA products which implement
the
Standard Disk Interconnect (SDI).
DSA defines the operating
rules of mass storage subsystems and how they interface with
the
host
computer.
Some
of
the characteristics of DSA are listed
below.

I/O management

has

been

moved

from

the

host

the

controller.

The

host

views

the

disk

subsystem

one

contiguous

string
of
sectors
known as logical blocks.
block contains 512 bytes of information.
o

The

host

- cylinder,
o

Host

and

Storage

1.3

MASS

STORAGE

The

KDA50-Q Disk
(MSCP)
device.

intelligent

not

concerned with

track,

sector,

subsystem

Control

such

exchange

messages

use

the

Mass

PROTOCOL

Controller

mass

geometry

etc.

Protocol.

CONTROL

MSCP

disk

A logical

is
a

storage

a Mass

Storage
Control
communication
protocol

controllers.

MSCP

Protocol
used with

hides

device-dependent requirements,
such
as disk geometry and error
recovery strategies, from the
host.
It
thus enables
several
different device drivers to be replaced by one class driver.

To request an I/O operation,

the host constructs an MSCP

message

and
sends
it
to the controller.
The MSCP message contains the
drive address, the function to be performed, the starting logical
block
number
(sector),
and
the amount of data requested.
The
message does not contain drive geometry information because
MSCP
hides device dependant requirements.
When the subsystem receives
the request, it performs all drive management and data
movement,
as
well
as
any
necessary
recovery,
independently.
Upon
completion, the subsystem sends the host an MSCP response message
giving
status
information.
This flow differs from conventional
subsystems, in which host computer resources
would
be
wused
to
control the drive.
One recovery technique is called revectoring,
when the KDA50-Q accesses a replacement
sector
instead
of
the
original
sector
previously
found
to be in error.
A sector is
marked as bad, and replaced via a cooperative process between the
host software and the KDA50-0Q.

INTRODUCTION

1.4

The

KDA50-Q MODULES

following paragraphs describe

module

and

the processor module.

l1.4.1

The

SDI

the

hardware

both

the

SDI

Module

The SDI module (M7165) is the the communication interface between
the
KDA50-Q
circuitry and
0

processor
module and the disk drives.
functions of the SDI module are listed

~a buffer

full

Converts

the

format
o

KDA50-Q

(serial)

Generates

the

error

bursts

The

buffer

the

format

(parallel)

SDI

vice-versa.
Error

Correction

correction capability of

per

including

block

(ECC).

to 8

10-bit

interface

to the

(sector).

real-time
error

Code

and electrical

detection

the

SDI,

and

RAM.

Processor Module

The processor module

(M7164)

KDAS50-Q.
Some
of
the
module are listed below.
o

and

real-time

code has

Implements

which
improves
revolutions due to

condition.

This

SDI,

1.4.2

the

Contains a 32K byte
high
speed
buffer
that
is
wused
during
data
transfers.
The
buffer
allows
controller-to-drive tranfers to occur at a
higher
rate
than
controller-to-host
transfers
performance by minimizing missed disk

Some of
below.

Performs

all

the

circuitry and

KDAS50-Q

control

functions

interaction with

portion
of

the

via

two

the processor

QBUS

registers;
the
1Initializing
and polling (IP) register
and the Status/address (SA) register.
A switch pack
is
used to set the I/0 page register address.

Reports microcode detected errors through four
LEDs
on
the
processor
module
and four LEDs on the SDI module.
The error code reported indicates the module to replace.

Also

located

the

processor

module

‘a

dual

microprocessor.
It
is
made
up
of
two
12-bit
microprogram sequencers which share a common 16-bit ALU.

INTRODUCTION

The
combination
of
the
sequencers and the shared ALU
creates a dual microprocessor capable of
executing
two
independent,
interleaved
microprograms (from Read Only
Memory)
at
the
same
time.
One
of
the
sequencers
controls
the
KDA50-Q to host interaction and the other
controls the KDA50-Q to
disk
drive
interaction.
For
greater efficiency, one sequencer fetches an instruction
while the other executes an instruction.

1.5

KDA50-Q FUNCTIONAL MICROCODE

The functional microcode can be divided into two functional flows

or streams.
The QBUS control stream which manages the controller
to host interface and the drive control stream which manages
the
controller to disk

1.5.1

QBUS

Some of
listed

drive

Control_Stream

the functions that the QBUS Control Stream
below.

o
"

interface.

performs

are

Tracks
to
the
appropriate
handling
routine
in
the
microcode
when
the
host
has a command to send to the
KDA50-Q or the KDA50-Q has a response
to
send
to
the
'

host.

Exchanges

information packets with the host

Validates

each packet

Constructs the KDA50-Q response packets for transmission
to

the

from the host.

host.

Analyzes the drive packets and
listed

performs

the

functions

cylinder,

below.

‘0

Decodes the logical block number (LBN)
group, track, and sector information.

Optimizes

seek

selection

commands.

in memory.

Allocates data buffer space.

1-4

from

the

outstanding

INTRODUCTION
o0

Computes

and

stores

packet

error

parameters

for

each

sector

transfer.
0

Performs

Performs memory mapping

Transfers data between
(including
automatic
memories).

Performs

ECC

Polls the

error

detection.

for mapped

requests.

the host and internal
memory
support
for
block
mode

correction.

command

queue

the

completion

each

command.
0

Performs

1Initiates

1.5.2

Drive

initialization.

Drive

Control

Monitors

Stream packet

executions.

Stream

Some of the functions
listed below.
O

Control

that

the

ATTENTION

Drive

from

Control

the

Stream performs
.

drives.

When

attention
has
been
detected, the Drive
gets the drive status, compares
it
with
status, and takes the appropriate action.
o

Constructs

packets

and

may

sends

packets

the

write,
replace,
etc.)
attention condition.

the

packets

disk

host

response

from the

drive

Control Stream
the
previous

drives.

request

The

(read,

drive

Receives

Monitors the drive status flags from
the
QBUS
Control
Stream,
- The
drive
status
flags
are
used
for
communication between the QBUS control
stream
and
the
Drive Control Stream.
_

and validates

result

are

Performs tasks as required by the

Some of

these

tasks are

drive

listed below.

1-5

drives.

status

flags.

INTRODUCTION

Initiates read, write,
to

the

Reads

seek,

and head select packets

drive.
and verifies
the block

(sector)

Performs data transfers between

header,.

internal RAM and

the

disk drive.

1.6

Updates drive

status

Performs data error analysis

Performs

bad block

and buffer-use
and

flags.

recovery.

revectoring.

KDAS50-Q SPECIFICATIONS

The KDA50-Q Disk Controller Specifications are described

in Table

1-1 .

Table

1-1:

KDA50-Q Specifications

Characteristics

Specifications

Physical

KDA50-Q processor module (M7164)
KDA50-Q SDI module (M7165)
50-pin flat cable assembly
40-pin flat cable assembly
SDI cable assembly
1/0 bulkhead assemblies

Power

components

consumption

Heat dissipation
" Electrical
voltage
and
current
requirements

Operating
range

nominal

Approximately

238.6

Btu/hour

13.5 Amps at +5 Volts,
at +12 Volts

3.0
AC
(total)

QBUS Loading

temperature

67.9 Watts

0.5

30 milliAmps

standard

loads

10 C to 40~ C (50" F
to
104~
with a temperature gradient of
C/hour (36~ F/hour)

F)
207

INTRODUCTION

Table

1-1

(cont.)

~haracteristics

Operating

humidity

Specifications

relative

10%

range

Operating

90%

temperature
minimum dew

altitude

Sea

level

with

of 28~ C
point of

wet

(82~
2~ C

2400 meters

(8000

Derate
the
maximum
operating
temperature

range

bulb

F) and
(36~ F)

ft).

allowable
by
1.87

C/1000 meters (1~ F/1000 feet)
operation above sea level

for

~ounting

Mounts

SPC

restrictions

slots

two quad-height QBUS

the

following

mounting

boxes:

BAll-S

BA23
Bulkhead

Two

requirements

Two

1.7

You

DIGITAL CUSTOMER SERVICE

can

upgrade

your

maintain

optimum

advantage

l.7.1

one

Hardware

Add-on

and

recommend

DIGITAL

CPU
the

field

cutouts
standard

for

system
service

smoothly

and

of
your
new
options listed

or -N,

for

H3490

efficiently

system
below.

your

service

services

and

taking

get

you

started.

2, 'Physical connection of
system

strongly

new
CPU upgrade be installed by qualified
technicians.
1Installation includes:

Pre-installation evaluation to ensure
a
environment including power, temperature,

full

BAll-S

cutouts

Services

upgrade
that

2x3"
3x2"

with H3490

CONTRACT OPTIONS

performance
of

or -N
(rackmounted)

equipment

functionality.

and

suitable
site
and humidity.

verification

INTRODUCTION

Maintenance services keep you going.
Once your upgrade has
been
installed
by
DIGITAL
field service, the entire upgraded system
will be eligible for coverage by one
of
the
following
DIGITAL
comprehensive service contracts.

DECservice - A comprehensive
on-site
service
provides
committed
response
times,
continous
effort until the
problem is solved, a program of preventive
maintenance,
installation
of
the
1latest
engineering
changes, and
automatic escalation for complex problems.

Basic Service An
economical
full
service
coverage
provides
priority
status,
second
only
to DECservice
calls, and you get the
preventive
maintenance
on-site
services listed above.

For less comprehensive
but
equally
reliable service
you
can
choose Per Call Service, Carry-In Service or DECmailer Service.

’1.7.2

Software Services

If your need is
to
analyze
your
current
system,
develop
or
implement
software,
or
upgrade
your
existing system, DIGITAL
offers a service to meet your needs.
The following services will
be
of
particular
interest
to
you
as
you
plan to add on or
upgrade.

1.) Computer Performance Service - Helps you develop
plans

problems

identifying

growth

add-on or upgrade options before

begin.

System Staft-up Service Packages -

Consulting Services - Provides software
programming
project
manager
expertise
on a resident, per-call,
fixed-price basis.
Your choice.

training
services.

for

your

staff

and

Provides

one

year

fixed-cost

support

or
or
|

Whichever DIGITAL service option you
select,
you
will receive
high
quality,
reliable
service from one of the largest service
organizations in the industry.
For more information,
call
your

1-8

INTRODUCTION

local DIGITAL field

1.8

service

office.

RELATED DOCUMENTATION

DIGITAL

customers

may

order

the

following

KDA50-Q

manuals.

KDA50-Q SERVICE MANUAL (EK-KDA5Q-SV)

KDA50-Q

Employees:

FIELD MAINTENANCE

PRINT SET

(MP-01423)

The User Guide and Service Manual may be
ordered directly from Publication and
Circulation Services, 10 Forbes Road,
Nothboro, Massachusetts 01532 (RCS Code:
NR12, Mail Code:
NRO3/W3).

The Field Maintenance Print Set can be
ordered directly from the Software
Distribution Center, 444 Whitney Street,
Northboro, Massachusetts 01532 (RCS
Code:
MSDC, Mail Code:
NRO2-1/J6).

Non-Employees:

Outside

the

The

above documents can be ordered
directly from Digital Equipment
Corporation, P.O.
Box CS2008, Nashua,
New Hampshire 03061, or by calling toll
free:
800-258-1710.

United States,

consult

local

1-9

DIGITAL offices.

CHAPTER

INSTALLATION

2.1

INTRODUCTION

The

KDA50-Q

variety

two

board

CPU

disk

controller

packages.

that

Although

can

these

installed

packages

are

different,
the
KDA50-Q
1installation
procedure
for
them
is
similar.
The differences will be called out where needed.
Table
2-1 lists these packages and the KDA50-Q assembly to be used with
them.
Table

2-1:

KDAS50-Q Assemblies

CPU Package

KDAS0-Q

Assembly

BAll -S or -N (5 1/4"
BA23 with H3490**
Alternate

The

size

Part

KDA50-0A

Installation Package

KDA50-0B

BAll

MASSBUS

box uses an I/O panel which has cutouts

cable

shown

BOX)*

wuse.

These

in Figure

cutouts must

adapted

intended for
to

2x3

cutout

2-7.

needed,

please also order BA23 Expansion Rackmount Package,

Number

[TBD],

when

installing

this

assembly.

This package

permits the optional addition of a second rackmounted BA23 with a
QBUS
expansion
kit.
This
cabinet, the BA23 rackmount
bulkhead.

package
kit,
and

includes the BA23 expansion
the
H3490
expansion
1/0

The
installation
procedure
for
the
KDA50-Q
Disk
Controller
requires
the
insertion
of
two quad-height modules into a QBUS
backplane.
These two modules are inserted in adjacent
slots
so
the
intermodule
<cables
can
be connected between them.
An I/0
bulkhead must be installed in the cutout provided at the rear
of
the
CPU
cabinet
wunless
the
alternate installation procedure,

INSTALLATION

described

section

2.4,

1is

|used.

internal

connects
the
modules
to the I/O bulkhead.
The
then
connected
to
the
I/0
bulkhead.
Figure

illustrated parts breakdown of

the

2-1:

SDI

cable

drives
shows

KDA50-Q assembly.

“oile.

Figure

disk
2-1

KDAS0-0Q Illusfirated Parts

are
an

‘

M7es

INSTALLATION

The KDA50-Q modules may be installed horizontally
or
vertically
depending
on
the CPU package used.,
1If the CPU package requires
the horizontal insertion of modules, the following checklist
may
still
be
wused
by considering module M7164 the top module.
The
following installation checklist indicates where
each
procedure
is described.
o

Check

the

panel

requirements

for

Check

the

address

Connect

power

needs,

I/0 page

the

your

and

cables
(2.2.3)

Insert module

M7164

into

OQBUS

1loading,

(Table

1-1)

switches

and

jumper

40-conductor

intermodule
respectively

system

and

module

the

first

the

M7164

(top

(2.2.1)

50-conductor

(J2)

and

left)

~vacant
backplane
slots
and engage the handle
latches.
Leave the 50 conductor cable
on
top

handle retainer latch.

Insert

and

Slide

Connect

both

backplane
o

clamp

(J4).

the

internal

SDI

cable

the

40-conductor

and

cables

to module

(2.2.5)

Press M7165 into
retainer latches.
If

(2.2.4)

one-half

slot

intermodule

the

M7165

standard

M7165

the
backplane,
(2.2.7)

(J4)

two

retainer
of
the

to module

M7165

way

into

the

50-conductor

(J3

and J1)

engaging

installation package

and

the

used:

second

(2.2.6)

handle

install

the
1I/0 bulkhead connector assembly, route the internal
SDI cable ends to the bulkhead location, and connect the
external
assembly

SDI
(2.3)

cables

(from

DSA disks)

the

bulkhead

If the alternate installation package
1is
used:
mount
the
alternate
bulkhead
assembly, connect the internal
SDI cable ends to the bulkhead assembly, and connect the
external SDI cables (2.4)

Perform

the

field

acceptance

test

procedure

(2.5)

INSTALLATION

NOTE

The

position

reversed.

the

Ensure

KDA50-Q0

that

the

modules
top

can

left

module

initially
installed
has
the
40-conductor
and
50-conductor
flat
ribbon cables attached.
Also
ensure that the 50-conductor
flat
ribbon
cable

connected
the module

. .2

to the
handle

MODULE PREPARATION

following

modules,

2.2.1

AND

paragraphs

I/0 bulkhead,

1I/0 Page

Address

second module is not
retainer latches.

INSTALLATION

describe

and

crimped

how

install

the

KDA50-Q

cables.

Switches And Jumper

The KDA50-Q Disk
Controller
contains
two
registers
that
are
visible
in
the I/0 page.
They are the initializing and polling
(IP) register and the status and address (SA) register.
The
1IP
register
1is
Tassigned
the default octal Q-BUS address of 172150
(F468 Hex).
The SA register address is the IP address plus 2.
NOTE

QBUS address bits 13 and above in the IP register
are unadjustable and are automatically assigned a
value of 1.

The

QBUS

address

selector

switches

and

jumper

(Wl)

are

used

set
the QBUS address for the IP register.
The location of these
switches and the jumper on KDA50-Q module
(M7164)
1is
shown
in
Figure
2-2.
Set
the
QBUS
address switches and jumper to the
" positions shown in Figure 2-3 to select octal QBUS address 172150
(F468
Hex).
This address is the default value shipped with the
KDA50-Q (jumper Wl is installed).
Alternate octal addresses
for
the
1IP
register
are:
160334 (EODC Hex) and 160340 (EOEO Hex).
(Jumper W1l should be removed).
If you are unsure of
the
switch
operation refer to Figure 2-4.
NOTE

W2 and W3 must be removed for
Q22/CD
backplanes
and left installed for Q22/022 backplanes on both

2-4

INSTALLATION

modules

M7164

(refer

(refer to Figure

Figure

2-5).
5

2-2)

and

M7165

INSTALLATION

Wy In =1

b ‘ I Spd‘ 13 12
-Baogggss
Gits ‘*%J\M
12{

Lid

TGS

v 4 oyt = ¢

A18 1 b|S 4 3|21 0

codg '\f7
-/
2 | |
=3
O
BINARY |
c,o:e*‘l:ll ({ (Ot ojoo (|l O (|]OLoOr
50
OCTAL

[QORSOHF|11
switch

§efimq

Wi |Sl S2 53| s¥ S5 56| 571 S8 8

IN |orF oN OFF] ofFr orr on| BN OFF O OFF

ALWARYS

‘

2evos

RLWnYs owes

Figure

2-2:

M7164 QBUS Address

switch and Jumper Locations

B 50G
T
Pim
piw
YoSR

=
m?mvzez

M716Y

| ‘

123¥T 679410

Tum

’

Figure 2~-3:

(uuumu":p

g ,_L
M
(Wf 'k"src

;

KDAS50-Q Sw1tch Setting for Address

2-6

["'yvi

Wfi]

w;wz

172150

'%
(F468 Hex)

INSTALLATION

modified rocker:

rocker:

slide

eoffposttton

- 'B'Ff position

red band here

on position

red band here

are shown in the off position, and switchp is shown in the on
Note: In each picture, switches 1 through#
Figure 2-4:

position.

Address Selector Switch Operation

0000000000000000000000

000000000000000000000000000

oe s:%.“z::xmwaz:sfij

M6y

:fiUr?Q r

|
L

R R L] T SR WL
Wfifl

— CLoN | CLON| I

T ) S

lecations
2

Ewél?i‘:lfl
% Efi‘éflé”fl”&

=T
P

NOTE

be
should
The QBUS address switches and jumpers
set
for
a
floating
address
when a second DSA

To
system.
a
on
installed
is
controller
determine
a
floating
address, check the system

2-7

INSTALLATION

configuration
already
addresses
Hex).

In past

disk products,

selectable.

This

A typical

vector

KDA50-Q by

the

2.2.2

and QBUS

installed.
are 160340

QBUS

Sometimes

addresses
of

Common
(EOE0 Hex)

vector

all

devices

floating
and 160330

address

was

octal
(EODS

also

physically

is not true with the KDA50-Q Disk Controller.

address

154

(octal)

will

supplied

the

late

reduced

software.

Tuning

a QBUS

system will

experience

data

performance
conditions
that can be remedied by tuning the QBUS.
This process involves changing
the
relative
positions
of
the
Direct
Memory
Access (DMA) devices on the bus, or making use of
other product features.
The device electrically nearest the host
processor has the highest priority; the device farthest away from
the

host

processor

2.2.2.1

OQBUS

Non-DMA

interfaces

has

Device

the

lowest

Positions
in

priority.

QBUS

should

usually

placed

electrically
nearest
to
the
host
processor since they do
signficantly affect the performance level of DMA devices.
The

proper positioning
several considerations.

The

instantaneous

DMA

devices

bandwidth

the

requirements

OQBUS

the

not

involves

device

interface.

Faster raw bandwidth devices typically require a
higher
priority, though this higher priority requirement
can be
offset by buffering in the interface which
reduces
the
instantaneous bandwidth requirements from the interface.
Interfaces with little buffering may
require
that
the’
instantaneous
bandwidth
match
or exceed the effective
bandwidth for the device.
:

While the KDAS50-Q interfaces
to
some
very
fast
disk
devices,
it
1is well buffered internally (which results
in a relatively low instantaneous bandwidth requirement)
and
operates
dependably
at
the
very end of the QBUS
(lowest priority).
The
KDA50-Q0
will
wait
very
1long
periods
of
time to gain access to the bus, and proceed

INSTALLATION

from this waiting period without

The amount
during

Devices

each

time

bus

that

the

error.

interface

occupies

the

QBUS

time

access.

hold

the QBUS

for

longer

periods

should
wusually be placed at a lower priority,
the time that a higher priority
device
must
gaining access to the QBUS.

to reduce
wait
for

The KDA50-Q occupies the bus according to the setting of
the
Burst
rate
parameter given to it by the operating
system.
The default value of four
1long-words
(8
word
transfers)
results
in
occupying
the
bus for a value
which
1is
carefully
chosen
to
provide
a
compromise
between a small bus occupancy time and a higher level of
performance resulting from transferring
more
words
in
every
bus
acquisition.
The
default value encourages
placing the KDA50-0Q towards the end
of
the
QBUS,
but
ahead of devices with longer bus occupancy times.
The
amount
of
time
re-requesting the QBUS

the
again.

interface

waits

before

Since all DMA
devices
must
wait
until
the
OQBUS
is
available,
a
higher
priority
device
which
requests
access rapidly may preclude a lower priority device from
accessing the QBUS for significant periods of time.
The KDA50-Q leaves a reasonable amount
of
time
before
requesting
the
bus for a successive transfer, and this
permits lower priority DMA devices to gain access to the
bus.
In
the interest of performance, this time is not
so large that a great many lower priority devices
could
be satisfied between two KDA50-Q requests. This KDA50-Q
successive transfer time
allowance
encourages
placing
the KDAS50-Q near but not at the end of the bus.
The average bandwidth

requirements

the

device

usage.

A more
frequently
used
device
1in
the
configuration
should
be
given a higher priority.
1In the QBUS, there
is some intrinsic delay in each bus cycle
according
to
how
many
higher priority interfaces the bus grant must
pass through before reaching the interface
which
wants
to use

the

bus,.

This consideration is highly application dependent,
but
it
would
be
expected
that
the large storage devices
connected to the KDA50-Q would be used frequently.
This

INSTALLATION

would

encourage

placing

the

end

Overall,
devices

the
as

recommendation
the
RC25
and

However,

not

place

the

bus

grants

are

2.2.2.2
The

worry

rate

the

Rate

overall

burst

system

parameter

end

Parameter

how many

efficiency

to a

number

default

value

large majority

2.2.3

The

M7164

four

the

Intermodule

increases

may

other

than

become

bits)

increasing

one.

the

devices

the

However,

increasingly

must

Cable

host

KDAS50-Q

chosen

KDA50-Q

data

late

likely

suit

Installation

interconnected

inner

M7164

you

that

the QBUS.
The
default
from one to eight.

(J1).
module

settable

(32

cables as shown in Figure 2-6.
flat ribbon cable that connects

M7164

force

(assuming

system configurations.

KDA50-Q modules

The

details

bus

value

flat
ribbon
50-conductor
connects

from

long-words

greater

conditions (on other devices)
the parameter is increased.
The

away

KDA50-Q).

parameter

indicates

configuration

very

will attempt to transfer when it accesses
for this parameter is four, but can range
The

further

is to place the KDA50-Q ahead of such
RQDX,
and behind other DMA devices.

physical

Burst

KDA50-Q burst

that

passed

KDA50-Q

QBUS.

KDA50-Q

software

the

(J2)

first.

cable

to M7165

a 40-conductor
(J3).

1Install

two

inch

1long

The outer cable is a
M7164 (J4) to
M7165

flat
the

ribbon

cable

two

cables

that
on

INSTALLATION

MTIES

///M

Figure 2-6:
2.2.4

KDA50-Q Intermodule Flat Ribbon Cables

M7164 Module Installation

At this point, module M7164 should have
two
intermodule
cables
attached
to
it
and
the
I/0
page address switches and jumper
should be properly

Ensure

that

grouping

set.

previously

inserted

modules

form

continuous

in the backplane.

Insert M7164 into the first of two vacant backplane slots.
slot should be the top or left backplane slot of the pair.

Press M7164 into the backplane and
latches.

the handle

2.2.5

engage

the

handle

This

retainer

Ensure the 50-conductor flat ribbon cable is on top of
retainer latch.

M7165 SDI Cable Installation And Initial M7165 Insertion

Insert plug P4 of the internal SDI cable assembly into
connector
J4
on
KDAS50-Q0 module
M7165 as shown in Figure 2-7.
Slide the
cable retainer over connector J4 until
the
connector
protrudes
through
the
plastic cutout.
The cable retainer should lock the
SDI

cable

in place.

2-11

INSTALLATION

gw;::"c{

SDt

¢cABLE

\{i
’;:—'.;fiaa

FYC"’“

Figure

2-7:

Slide M7165
slot.

Sipe View

View

M7165 SDI

Cable Assembly Installation

approximately one-half

the

way

into

the

backplane

INSTALLATION

2.,2.6

M7165

Intermodule

Cable

Installation

T~estall the 40-conductor flat ribbon cable on module

and
the 50-conductor
Figure 2-6.

2.2.7
Tress

Final
M7165

M7165
into

flat

ribbon cable

the

backplane

the handle
secure and

retainer latch.
Also
none of the cables are

‘Use

the

assembly.

2.3.1

the

and

Ensure

STANDARD

M7165

(J1)

(J3)

shown

Installation

latches.

2.3

on M7165

50-conductor

INSTALLATION

following
|

1I/0 Bulkhead

engage

flat

the

ribbon

handle

cable

retainer

top of
ensure
both
modules
are
now
crimped by the latch handles.

PACKAGE

procedures

when

installing

the

KDA50~-QA

Installation

An I/O bulkhead connector must be installed on the I/O
panel
at
the
rear of the CPU cabinet.
The connectors are designed to fit
in standard Digital Equipment Corporation 2x3
cutouts
(used
on
most of the newer systems).
If the system is installed in a BAll
box, an adapter plate must be installed to convert the
existing
I/0 panel cutout to standard 2x3 cutout size.
If an
Cable

I/0 panel is not available,
Installation section 2.4.

refer

the

Alternate

SDI
-

Each
bulkhead connector
will
accept
two
disk
connections.
Install
both
bulkheads and connect the internal SDI cables even
if some parts will initially be unused.
After the bulkheads have
been installed, route the SDI cables to the bulkhead location.

Use the following procedure to install
assembly if an I/0 panel is present.
1)

the

I/0 bulkhead connector

If the BAll box is used, a 2x3
adapter
plate
must
be
used
to
change
the
existing
1I/0 panel cutout to 2x3
cutout size.
The adapter plate attaches on
the
inside
of the I/0 panel.
Refer to Figure 2-8.

2-13

INSTALLATION

Using four sem screws, attach the bulkhead
assembly
to
the I/0 panel.
Make sure the EVEN marking is at the top
or left as viewed from the outside
of
the
1I/0
panel.
Refer to Figure 2-9.
‘
'

gan {SO(";A/
Adagtor Plate

'.f/(_; Pap&‘ (EY‘R(;O()

figm( 1= &)
BAll

2x3

Adapter Plate

Installation

."/l
. )
\
ehXeOI8

Figure

2-9:

2.3.2

1Internal

Install

the

Bulkhead

using

Note

the

cable

I/0 Panel Attachment

Cables

internal

assembly
how

SDI

cables

from the module

following

procedure.

Refer

ends

connectors

are

and

the

bulkhead

Figure

keyed

for

2-10.
correct

alignment.
Attach the cable ends and the pigtail ground clips of
the internal SDI cable assembly to the bulkhead assemblies.
Port
0
(as viewed from the exterior) is located on the top or left of
the bulkhead. Refer to Flgure 2-11.
The
not

internal

SDI

necessary

for service
attached.

cable assemblles
secure

access)

extra

is present,

have

cable.

the

been created
If

internal

2-14

cable

SDI

so that

retractor

cable

(used

should

INSTALLATION

\{.

)

‘

o“

)

('/"Y-HCQ‘ A hjr\.rmrs"%’ Rfi

mgrm&rl’

Figure 2-10: Internal SDI Cable Installation

° be SH@?'!(J)

Bk\kk;;\ |

C’LML! Y)
1o,

P.' .

JQ;ctbHEQ /7

(/‘3 Puir
611;\(.\0(

Figure 2-11:

Grounding Internal SDI Cable(s)

External SDI Cables

2.3;3

Refer to Figure 2-12 while completing the following procedure.

Plug the external SDI cables into the I/O bulkhead(s).

Secure the cables using the screw connections.

If the external cables connected to the I/0 panel have
following
the
use
bend horizontally,
their natural
securing procedure.

Refer to Figure 2-12.

Run the cables horizontally to a vertical rail.

2-15

INSTALLATION

Twist the
rail.

Tie

the cables

the

external

vertically,

cables

secure

and

route

the

cables
the

them vertically down

vertical

have

cables

Any cables that go to drives

rail.

their

that

the

base

are

natural
of

in the

the

same

bend
cab.

cab as

the
CPU
should
have any extra cable length secured so
that it will not interfere with the normal operation and
servicing of the drive.

VERSIONS

Figure
2.4

2-12:

ALTERNATE

External

SDI

INSTALLATION

Cable

Installation

PACKAGE

If an I/O panel is not present or if a

cable

should

required,

used

very

the KDA50-Q alternate

(Part Number

1long

internal

SDI

installation package

KDA50-QB).

If 2x3 cutouts are available, use the

installation

in the

I/0 Bulkhead Installation section above.

2.4.1

Mounting The Alternate Bulkhead Assembly

instructions

Use the following procedure only if it is impossible to mount the
bulkhead to an I/0 panel using a KDA50-QA.
Refer to Figure 2-13.

Select a
suitable
1location
on
either
rear
vertical
cabinet
rail
where
the
alternate I/0 bulkhead can be
mounted without
interfering
with
existing
equipment.

2-16

INSTALLATION

Choose

the

Push on
the

lowest

the

four u-nuts

vertical

Select

the

Mount

cabinet

1/2

rail

best

terminator

Phillips

available

head

the

sems

with

mount

rail

the

them with

vertical

(10-32

cabinet.

the

holes

1in

and

the

vertical

rail

to align

bracket.

angle

onto

location

1/2

the

bulkhead

rail

bracket

shield
with

two

inch).

bracket

four Phillips

onto

head

the

sems

vertical
(10-32

inch).

Assemble

the

bulkhead

assembly

2-17

shown

in Figure

2-13,

INSTALLATION

Cf‘:’yfi?ircu

NN
o

Figure

2-13:

Alternate Bulkhead Assembly

INSTALLATION

2.4;2

Internal SDI Cable Installation

Install the internal SDI cables from the module to
the
bulkhead
assembly
wusing
the
following procedure.
Refer to Figure 2-~10.
Note how the cable ends and
connectors
are
keyed
for
correct
‘alignment.,
Nli'd'”.n

Connect

(as
left

2.
3.

The

internal

Secure the internal
retainer

2.4.3

the

cables

the

exterior)

located

bulkhead.

Port

on the

top or

SDI

cables

the

1inside

cable

bracket.

Secure any extra
vertical rail.

internal

SDI

cable(s)

the

cabinet

External SDI Cable Installation

external

mounting

the

procedure

Plug

SDI

cables must

shield
install

grounded

terminators
the

the first

cables.

SDI

bulkhead
connector
connections.

‘

SDI

viewed
from the
of the bulkhead.

with

the

screws.

I/0O
Use

bulkhead
the

Refer

Figure

cable

into

the

bottom

right

and

secure

cable

using

the

Install an SDI cable for each disk
I/0 bulkhead connector 3

and moving

following

2-12.

drive,
to 0.

1I/0
screw

starting

NOTE

One

useful

practice

connect

drive

KDA50-Q
port
O
and drive 1 to KDA50-Q port 1,
etc.
However, it actually does not matter which
drive
connects
to
which
KDA50-Q
port.
The

KDA50-Q treats each port equally and obtains
unit number for each drive from that drive.

Install

the

the drive end of the SDI cables into
the
drive
I/0
bulkhead
connectors as described in the disk drive
user guide.

INSTALLATION

In most

cases,

the

provisions

already

provided

with

should
be used to secure the exterior SDI cables.
have not been provided, the exterior cables should
the backframe using cable tie(s).

2.5

FIELD ACCEPTANCE

TEST

Run

three
the

box

PROCEDURE

The field acceptance and test
Subsystem has

the

If provisions
be secured
to

procedure

for

the

KDA50-0Q

Disk

parts.

KDA50-Q

Disk

Controller

resident

diagnostic

test.

Run

the

disk
3.

After each

the

field

acceptance

has

host-resident
third

part

diagnostics

KDA50-Q

test

found

the

guide.

subsystem device

the

KDA50-Q-resident

applied

drive

user

KDAS50-Q

complete

The

disk

drive

Disk

this

are

Controller.

been

tested

diagnostics

separately,

are

run

power

|is

procedure.

1initiated
The

CPU

when
should

halted

during this test.
The four LED indicators on each KDA50-Q module
should display a cycling pattern in the LEDs.
Refer to the third
comment following Table 2-2.
The cycling
pattern
in
the
LEDs

signifies the completion of a successful KDA50-Q diagnostic test.
Figure 2-14 shows the location of the four LEDs on
each
KDA50-Q
module.
-

2-20

LAdNOLALLAL LUN

Leds

[ r:p\{fie/

soeel
2 L i
Ho-P )

M 716

-—

W37

Leds

r\/\/\0000

M71b5
i

Figure

2-14:

Diagnostic

Table

applied,

2-2:

LED Locations on KDA50-Q Modules

If the KDAS50-Q LEDs do not

power is
problem,

look up

LED Error and

display

the

LED code

cycling

in Table

2-2

M7165

LEDs*
8 4 21

0001

0010

0000

Hex 2; microcode stuck
init step 2
|

0011

0000

Hex 3; microcode stuck in

X X

after

locate

the

Symptom Codes

M7164

pattern

Error Symptoms

Most

Hex

init

Likely
Failure

undefined

step

2-21

Undefined

M7164
or
software

* *

INSTALLATION

Table

2-2

(cont.)

M7164

M7165

LEDs*

LEDs*
8 4 2

Error Symptoms

Most

Likely
Failure

Hex 4;
init

microcode
step
4

stuck in
or
QBUS

timeout error

Hex 4/5; test complete

Hex

undefined

Undefined

Hex

undefined

Undefined

Hex

wrap

Eo T

problem

»x
o

inactive

Normal display for
operating KDA50-Q

M7164
host

bit

set

TM)
oV
-

board

two

error

M7165

Hex

undefined

Hex

Many

RAM parity

error

M7165

ROM

error

M7164

Hex

sequencer

Hex

Cycling

Cycling
pattern

Undef ined

Timeout error,
check
error
code
in SA
register
(Refer
to
KDA50-Q Service Manual)

o N
o O

- O

o X

b A

o
X

O
O
- N

O o o
[

M7164

error

[

OO
[l o
[

one

parity

None

software

board

pattern

M7164

Hex

ot
o

=
%

oo
(= Ne
®x O

»
-

)

»
L
(]

O =

Hex

SA register

error

causes

M7164
No problem
* % %

2=-22

INSTALLATION

Table

2-2

(cont.)

M7164

M7165

LEDs*

Likely

Failure

***

Error Symptoms

Most

puring a cycling pattern,

the

LEDs

flash

one

time

starting

at the LSb and progressing through the MSb. These LEDs
begin
flashing
on the M7164 module, then progress to the M7165
module.,
However,
the pattern is executed very fast so it looks
like
all the LEDs are flashing at the same time. The flash goes
on
and
off
for
approximately
1/4 second and then repeats at
about a 4 second rate. The LEDs normally cycle while the KDA50-Q
is
waiting for the host to start the initialization process. At
that time, it responds to the
1initialization
and
the
cycling
pattern stops. This
the system software
the

normally occurs in about
is prepared to establish

four
seconds,
if
connection
with

KDA50-Q.

Note:

LED

OFF

May

When two codes are given for the same error, both
same

2.5.1
Each

OFF

indicate

the

failure.

Drive-Resident Diagnostics
disk

drive

should

tested

separately

running

the

drive-resident
diagnostics.
The
procedure
for
running
the
resident diagnostics is found in the installation chapter of
the
disk
drive user guide.
Perform the drive field acceptance tests
found in the installation chapter and then go to Paragraph
2.5.2
for the subsystem diagnostic procedures.

2.5.2

Subsystem Diagnostics

The subsystem diagnostic procedures for
the
KDA50-Q
controller
differ
when
they
are
used
on a PDP-11 CPU or a VAX CPU.
The
following paragraphs cover the PDP-11 diagnostics first and
then
the VAX diagnostics.
NOTE

the

diagnostic

the

KDA50-Q

program

Service

reports

Manual.

errors,

refer

INSTALLATION

CSR ADDRESS
NOTE:

VECTOR

(O)

LEVEL

NOTE:

154

(D)

DRIVE

CZUDI
HW

UNITS

UNIT

172150

KDA50-Q

NUMBER

CHANGE

(O)

The

automatically
of 4.

Sample

CONTROLLER

(D)

hardware
(L)

(D)

ignores

reassigns

the

this

question

appropriate

and

LEVEL

prompts:

CSR ADDRESS
DRIVE

NUMBER

CONTROLLER‘(O)

(D)

172150

)

CSR=1IP,

EXERCISE ON CUSTOMER DATA AREA (L) N ?
Sample

CZUDH

CHANGE
ENTER

software
(L)

MANUAL

prompts:

INTERVENTION

MODE

TEST

(L)

Sample CZUDI software prompts:
CHANGE

(L)

ENTER MANUAL INTERVENTION MODE FOR SPECIAL DIAGNOSIS (L) N ?
ERROR

LIMIT

(D)

READ TRANSFER LIMIT IN MEGABYTES - 0 FOR‘NO LIMIT (D) 0 ?
SUPRESS

PRINTING

INITIAL

ENABLE

WRITE

ERROR

LOG

SOFT

(L)

ERRORS

START

(L)

2-26

INSTALLATION

2.,5.2.2

VAX Subsystem Diagnostics

EHRAD (KDA50-Q Disk Drive Formatter)
EHRAD is
not
a
diagnostic.
specifically instructed to.

EHRAA

(KDA50-Q

Basic

EHRAA consists

three

Test

BUS

Test

Disk-Resident Diagnostic

Test

Disk

Functional

EHRAC

(Subsystem Exerciser Test)

aspects

both
upon

an operation.

enabled.

Check

tests:

Test

Exerciser Test)

SOFTWARE

depend

unless

Test

(Disk

System Clock

test

EHRAB

KDA50-Q

-on

following

Addressing

run

Diagnostic)

2.6.1

not

SYSTEM AND

Some

Subsystem

the

This program tests
type
disk
drive
differences in the

2.6

the read and write ability of any SDI
from
a
KDA50-Q,
and
will
display
read and write data to the operator.

CONSIDERATIONS

Or Timer
diagnostic
the

host

ability

and/or
of

the

recommended
processor

functional
host

that

usage

processor

clock

documentation

interrupts
for

time-out

appropriate

instructions.

2.6.2
The

Error

KDA50-Q

Logs
has

the

capability

return

information

the

operating
system for inclusion into an error log.
These entries
may include specific information on the operation of the KDA50-Q,
its
attached
drives,
or
other
parts
of
the
system
(host
processor, memory, software, etc.)
which
may
be
important
in
diagnosing
the
source
of possible problems.
It is recommended
that error logging be enabled in your operating
system
to
take
advantage
of
such
information.
Consult your operating system

INSTALLATION

documentation
error

logs.

Some

reports

for approrpriate

contained

the

information

error

log

may

the

enabling

changes

represent

the
configuration
or
operation
of
your
system
informational in nature, and thus may not represent the
of an error condition.
Examples of this may be:
0

completion

port
O

driver

and

the

sequence

between

the

KDAS50-Q
pertaining

(which

may

the

availability

result

changing

number)

Drive Numbering

DSA/SDI
be

initialization

attention messages

disk
drive
drive's unit

2.6.3

the

that
are
occurance

drives that
a
wunit

given

systems

sometimes
system

not

can be connected to the KDA50-Q
can
usually
number ranging from 0 to 254.
Some operating

support

only

documentation

this

supporting

for

how

for

entire

the

range

to 7.

appropriate

specify unit

unit

numbers,

Consult operating

capability,

and

drive

numbers.

The

unit numbers assigned to drives attached to a KDA50-Q0 do
not
imply
any
priority,
or
other special property; all drives are
treated equally by the KDA50~-Q.
The
only
requirement
on
unit
number
assignments
1is to avoid duplicating a unit number on two

different drives,
or

user,

its unit

The

number

which

KDA50-Q

could
will

duplicates

lead
not

confusion

permit

another

drive

drive's

application

accessed

while

the

number

second

drive
is also attached.
This situation may be corrected
changing either (or both) of the duplicating numbers.

Unit numbers can usually be easily changed at the drive, although
this
1is
recommended
only when the intended drive is not online
(not mounted by the operating system) to the KDAS50-Q.

2.6.4

System Performance And Operation

Consult
the
QBUS
sections
in
this
Chapter
for
information
pertaining
to
KDA50-Q
features and placement which may bear on
performance or operation of your system.