1.
SIGMA
9
SYSTEM
INTRODUCTION
The
XDS
SIGMA 9 Computer System
is
a
high-speed,
general-purpose
digital
computer system. It
is
designed
for a
variety
of
scientific,
business
data
processing,
and
time-sharing
applications.
A basic system includes a
central
prbcessing unit (CPU), a main memory subsystem,
and
an
independent
input/output
subsystem
..
Each major
system
element
performs asynchronously with
respect
to
other
elements.
The basic system can be
readi
Iy
expanded
to accommodate
the
user1s requirements. Main memory has addressing
space
for four million words. Memory access paths
can
be
in-
creased
from
the
basic two ports to a maximum
of
12
ports.
Input/output
capability
can
be increased
by
adding more
input/output
processors (lOPs),
device
controllers,
and
I/O
devices.
The CPU has a large instruction
set
that
includes
floating-
point
and
decimal instructions. A
special
feature
called
1I100k-ahead
ll
enables
the
CPU
to
overlap
instruction
exe-
cution
with memory
accessing,
thereby
reducing program
execution
time.
A large main memory
of
up
to 524,288
(512K) words
is
provided. The memory consists
of
up
to
16
modular units
of
32,768 (32K) words
each.
The number
of
ports
in
each
memory unit
can
be
expanded
to
allow
independent
access to memory by
up
to
12
processors -
either
CPUs or lOPs. Each bank
operates
asynchronously,
and
address
interleaving
can
be provided between
adjacent
banks. This multibanK, multiaccess memory subsystem with
interleaving
achieves
system performance far
in
excess
of
single
memory bank designs. The SIGMA 9 system
can
in-
clude
up
to
11
independent
I/O
processors (limited only by
port expansion
capability)
of
two types -multiplexor
I/O
processors
and
high-speed
RAD
I/O
processors -which
can
transfer
data
at
rates
up
to
three
million bytes per
second,
concurrent
with CPU instruction
execution.
The SIGMA 9 computer design
is
compatible
with
the
SIGMA 7 computer, so
that
SIGMA 7 programs will run
on SIGMA 9. Therefore, comprehensive, modular
soft-
ware,
requiring no reprogramming
is
avai
lable,
including
operating
systems, assemblers, compilers,
mathematical
and
uti Iity routines.
Reliabi lity,
maintainabi
lity,
and
avai
labi lity have been
significantly
improved
over
previous SIGMA computers.
A
partitioning
feature,
for
example,
permits faulty units or
an
entire
subsystem, consisting
of
a CPU, memory
un
it,
lOP,
and
attached
peripherals to be isolated
from
the
sys-
tem for diagnosis
and
repair
whi Ie
the
primary system
continues
operation.
This manual describes
the
general
characteristics
and
features, system organ
ization,
instruction
set,
I/O
oper-
ations,
operator
controls,
and
timing
of
the
system.
GENERAL
CHARACTERISTICS
A SIGMA 9 computer system has
features
and
operating
characteristics
that
permit
efficient
functioning
in
general-
purpose, multiprocessing,
time-sharing,
real-time,
and
multiusage environments:
•
Word-oriented
memory
(32-bit
word plus
parity
bit)
which
can
be addressed
and
a Itered as
byte
(8-bit),
halfword
(2-byte),
word
(4-byte),
and
doubleword
(8-byte)
quantities.
• Memory
expandable
from
131,072 (l28K) to
524,288
(512K) words in blocks
of
16,384 (16K),
32,768
(32K),
and
65,536 (64K) words. Expansion proceeds in 32K
blocks
from
128K to 256K,
and
in 64K blocks from
256K to 512K (where K = 1024 words).
• Direct addressing
capability
(real
extended
mode)
of
entire
memory.
• Indirect addressing with or without
post-indexing.
• Displacement index registers, automati
ca
lIy
self-
adjusting for
all
data
sizes.
• Immediate
operand
instructions, for
greater
storage
effi
ciency
and
increased
speed.
•
16
general-purpose
registers,
expandable
to
64
(in
blocks
of
16)
reduce
data
transfer to
and
from
reg-
isters
in
a multiusage environment.
• Hardware memory mapping, which
virtually
elimi-
nates memory fragmentation
and
provides dynamic
program
relocation.
• Four modes
of
memory
access
protection
for system
and
information
security
and
protection.
• Memory
write
protection
preventing
inadvertent
destruction
of
critical
areas
of
memory.
• Watchdog timer
to
assure nonstop
operation.
•
Real-time
priority
interrupt system with
automatic
identification
and
priority
assignment, fast response
time,
and
up to 238 levels
that
can
be
individually
armed,
enabled,
and
triggered
by program
control.
• Instructions with long
execution
times
can
be
in-
terrupted
to
guarantee
response
to
interrupts.
• Automatic traps for error or fault
conditions,
with
masking
capabi
lity
and
maximum
recoverabi
lity,
under program contro
I.
• Power
fail-safe
for
automatic,
safe
shutdown
in
event
of
power fai lure.
SIGMA 9 System
