<s>
The	O
VAXft	B-Device
was	O
a	O
family	O
of	O
fault-tolerant	B-General_Concept
minicomputers	B-Architecture
developed	O
and	O
manufactured	O
by	O
Digital	O
Equipment	O
Corporation	O
(	O
DEC	O
)	O
using	O
processors	O
implementing	O
the	O
VAX	B-Device
instruction	B-General_Concept
set	I-General_Concept
architecture	I-General_Concept
(	O
ISA	O
)	O
.	O
</s>
<s>
"	O
VAXft	B-Device
"	O
stood	O
for	O
"	O
Virtual	O
Address	O
Extension	O
,	O
fault	B-General_Concept
tolerant	I-General_Concept
"	O
.	O
</s>
<s>
These	O
systems	O
ran	O
the	O
OpenVMS	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
,	O
and	O
were	O
first	O
supported	O
by	O
VMS	B-Operating_System
5.4	O
.	O
</s>
<s>
Two	O
layered	O
software	O
products	O
,	O
VAXft	B-Device
System	O
Services	O
and	O
VMS	B-Operating_System
Volume	O
Shadowing	O
,	O
were	O
required	O
to	O
support	O
the	O
fault-tolerant	B-General_Concept
features	O
of	O
the	O
VAXft	B-Device
and	O
for	O
the	O
redundancy	O
of	O
data	O
stored	O
on	O
hard	O
disk	O
drives	O
.	O
</s>
<s>
All	O
VAXft	B-Device
systems	O
shared	O
the	O
same	O
basic	O
system	O
architecture	O
.	O
</s>
<s>
A	O
VAXft	B-Device
system	O
consisted	O
of	O
two	O
"	O
zones	O
"	O
that	O
operated	O
in	O
lock-step	B-General_Concept
:	O
"	O
Zone	O
A	O
"	O
and	O
"	O
Zone	O
B	O
"	O
.	O
</s>
<s>
Each	O
zone	O
was	O
a	O
fully	O
functional	O
computer	O
,	O
capable	O
of	O
running	O
an	O
operating	B-General_Concept
system	I-General_Concept
,	O
and	O
was	O
identical	O
to	O
the	O
other	O
in	O
hardware	O
configuration	O
.	O
</s>
<s>
Lock-step	B-General_Concept
was	O
achieved	O
by	O
hardware	O
on	O
the	O
CPU	O
module	O
.	O
</s>
<s>
The	O
VAXft	B-Device
Model	O
310	O
,	O
introduced	O
as	O
the	O
VAXft	B-Device
3000	O
Model	O
310	O
,	O
code	O
named	O
"	O
Cirrus	O
"	O
,	O
was	O
introduced	O
in	O
February	O
1990	O
and	O
shipped	O
in	O
June	O
.	O
</s>
<s>
It	O
was	O
the	O
first	O
VAXft	B-Device
model	O
,	O
and	O
was	O
DEC	O
's	O
first	O
fault-tolerant	B-General_Concept
computer	O
that	O
was	O
generally	O
available	O
.	O
</s>
<s>
At	O
the	O
1991	O
launch	O
of	O
new	O
VAXft	B-Device
models	O
,	O
the	O
VAX	B-Device
3000	O
Model	O
310	O
was	O
renamed	O
to	O
follow	O
the	O
new	O
naming	O
scheme	O
,	O
becoming	O
the	O
VAXft	B-Device
Model	O
310	O
.	O
</s>
<s>
It	O
used	O
the	O
KA520	O
CPU	O
module	O
containing	O
a	O
16.67MHz	O
(	O
60	O
ns	O
cycle	O
time	O
)	O
CVAX+	B-Device
chip	O
set	O
with	O
32KB	O
of	O
external	O
secondary	B-General_Concept
cache	I-General_Concept
.	O
</s>
<s>
The	O
system	O
contained	O
two	O
such	O
CPU	O
modules	O
,	O
one	O
in	O
each	O
zone	O
,	O
running	O
in	O
lock-step	B-General_Concept
.	O
</s>
<s>
The	O
VAXft	B-Device
Model	O
110	O
,	O
code	O
named	O
"	O
Cirrus	O
"	O
,	O
was	O
an	O
entry-level	O
model	O
announced	O
on	O
18	O
March	O
1991	O
alongside	O
three	O
other	O
models	O
.	O
</s>
<s>
The	O
Model	O
110	O
was	O
essentially	O
a	O
low-cost	O
model	O
of	O
the	O
VAXft	B-Device
Model	O
310	O
,	O
and	O
had	O
a	O
theoretical	O
maximum	O
performance	O
of	O
2.4	O
VUPs	O
.	O
</s>
<s>
The	O
DEC	O
WANcontroller	O
620	O
was	O
designed	O
for	O
use	O
in	O
VAXft	B-Device
systems	O
.	O
</s>
<s>
The	O
VAXft	B-Device
Model	O
410	O
,	O
code	O
named	O
"	O
Cirrus	O
II	O
"	O
,	O
was	O
a	O
mid-range	O
model	O
announced	O
on	O
18	O
March	O
1991	O
alongside	O
three	O
other	O
models	O
.	O
</s>
<s>
Originally	O
supposed	O
to	O
ship	O
in	O
June	O
or	O
July	O
1991	O
,	O
it	O
was	O
delayed	O
until	O
September	O
1991	O
,	O
with	O
the	O
reason	O
given	O
by	O
DEC	O
being	O
that	O
it	O
wanted	O
to	O
tune	O
a	O
new	O
release	O
of	O
VMS	B-Operating_System
for	O
the	O
system	O
.	O
</s>
<s>
The	O
Model	O
410	O
was	O
identical	O
to	O
the	O
Model	O
310	O
,	O
but	O
used	O
the	O
KA550	O
CPU	O
module	O
containing	O
a	O
28.57MHz	O
(	O
35	O
ns	O
cycle	O
time	O
)	O
SOC	B-Device
microprocessor	O
with	O
128KB	O
of	O
external	O
secondary	B-General_Concept
cache	I-General_Concept
.	O
</s>
<s>
The	O
VAXft	B-Device
Model	O
610	O
,	O
code	O
named	O
"	O
Cirrus	O
II	O
"	O
,	O
was	O
a	O
mid-range	O
model	O
announced	O
on	O
18	O
March	O
1991	O
alongside	O
three	O
other	O
models	O
.	O
</s>
<s>
Originally	O
supposed	O
to	O
ship	O
in	O
June	O
or	O
July	O
1991	O
,	O
it	O
was	O
delayed	O
until	O
September	O
1991	O
,	O
with	O
the	O
reason	O
given	O
by	O
DEC	O
being	O
that	O
it	O
wanted	O
to	O
tune	O
a	O
new	O
release	O
of	O
VMS	B-Operating_System
for	O
the	O
system	O
.	O
</s>
<s>
The	O
VAXft	B-Device
Model	O
612	O
was	O
a	O
high-end	O
model	O
announced	O
on	O
18	O
March	O
1991	O
alongside	O
three	O
other	O
models	O
.	O
</s>
<s>
Originally	O
supposed	O
to	O
ship	O
in	O
June	O
or	O
July	O
1991	O
,	O
it	O
was	O
delayed	O
until	O
September	O
1991	O
,	O
with	O
the	O
reason	O
given	O
by	O
DEC	O
being	O
that	O
it	O
wanted	O
to	O
tune	O
a	O
new	O
release	O
of	O
VMS	B-Operating_System
for	O
the	O
system	O
.	O
</s>
<s>
The	O
Model	O
612	O
was	O
a	O
VAXcluster	B-Operating_System
of	O
two	O
VAXft	B-Device
Model	O
610s	O
with	O
an	O
expansion	O
cabinet	O
positioned	O
between	O
the	O
two	O
systems	O
as	O
standard	O
.	O
</s>
<s>
The	O
VAXft	B-Device
Model	O
810	O
,	O
code	O
named	O
"	O
Jetstream	O
"	O
,	O
was	O
a	O
high-end	O
model	O
introduced	O
in	O
October	O
1993	O
instead	O
of	O
the	O
targeted	O
introduction	O
date	O
in	O
the	O
late	O
summer	O
or	O
early	O
fall	O
of	O
1992	O
.	O
</s>
<s>
The	O
Model	O
810	O
was	O
a	O
third	O
generation	O
VAXft	B-Device
system	O
.	O
</s>
<s>
It	O
used	O
the	O
KA560-AA	O
CPU	O
module	O
,	O
which	O
contained	O
two	O
83.33MHz	O
(	O
12	O
ns	O
cycle	O
time	O
)	O
NVAX+	B-Device
microprocessors	O
with	O
512KB	O
of	O
B-cache	O
(	O
L2	B-General_Concept
cache	I-General_Concept
)	O
.	O
</s>
<s>
The	O
module	O
's	O
two	O
microprocessors	O
operated	O
a	O
in	O
lock-step	B-General_Concept
fashion	O
,	O
and	O
like	O
previous	O
VAXft	B-Device
systems	O
,	O
there	O
were	O
two	O
such	O
CPU	O
modules	O
in	O
a	O
system	O
,	O
one	O
in	O
each	O
of	O
the	O
two	O
zones	O
,	O
which	O
operated	O
in	O
a	O
lock-step	B-General_Concept
fashion	O
.	O
</s>
