2-10
Theory
of
Operation
The case has a door which can
be
opened
to provide access to the upper 9 slots or removed to
provide access to
all
12 slots. A dc box fan attached to
one
end
of the stack provides cooling air to
the boards.
The stack interconnects with the computer motherboard via two 25-pin connectors
and
a 50-
conductor input/output processor (lOP) cable. The 25-pin connectors on the bottom of the stack
interconnect with connectors
on
the computer motherboard when the stack
is
positioned
in
the
computer. These connectors provide power
and
control signals
and
send self-test information to the
system control module (SCM). The internal
lOP ribbon cable connects the motherboard to the lOP
board
in
slot
#2.
Additional lOP cables interconnect lOP boards
and
the computer rear panel.
Stack
Configurations
The stack has 12 slots numbered from 1 to 12, with slot # 1 the bottom slot
and
slot # 12 the top.
All
slots are interconnected by the memory processor bus via the stack motherboard. The memory
processor bus
(MPB), which has
32
data/address lines
and
12 control lines, interconnects
all
boards
to the
lOP board(s). The lOP board
in
slot
#2
is
connected to the internal lOP cable which
is
routed
to the motherboard.
Four types of boards can
be
used
in
the stack: central processor unit (CPU), input/output processor
(lOP),
and
random access memory
(RAM).
A load board may also be required, depending
on
stack
configuration.
All
are described
in
following paragraphs.
The stack can
be
configured with various combinations of boards.
One
or two CPU boards can be
added.
One
or two lOP boards can
be
added. Any number of
RAM
boards are allowed. However,
if 1 Megabyte
RAM
boards are used, they must be used
in
pairs.
The following rules must be observed for
all
configurations:
• Slot # 1 must always contain a CPU card.
• Slot
#2
must always contain an lOP card.
• If there
is
one
additional lOP board,
it
must
be
in
slot
#3.
If there are two additional lOP
boards, they must
be
in
slots
#3
and
#4.
• No empty slot
is
permitted between two finstrates.
• 1 Megabyte
RAM
boards must be used
in
pairs
(2,
4,
6, 8, or 10).
•
A load board must
be
used
in
the top occupied slot (adjacent to the
RAM
boards) any tirrle the
stack configuration
is:
a.
One
CPU,
one
lOP,
and
one
512K
RAM
card.
b.
RAM
is
composed of
all
1 Megabyte
RAM
boards
and
there are less than 6
RAM
boards.
(The load board
is
not required if other types of
RAM
are included
in
the stack,or there
are more than six 1 Megabyte
RAM
cards
in
the stack.)
Minimum
and
maximum configurations are as
follows:
Finstrate
Minimum
Maximum*
CPU
1 3
lOP
1 3
RAM
2
10
* Maximum of 12 finstrates
per
stack.
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