Table
26.
Functions of Memory Unit Configuration Control Panel
Row
(cont.)
Label
Switch/Indicator
STARTING
ADDRESS
7 switches
154 Configuration Control Panel
Function
Used
to
set
the
starting addresses of
the
memory units.
From
left
to
right
the
switches
are
labeled S12, S13, S14, S15, S16, S17, and
S 18. Using
the
switches as a 7-position binary
field,
this allows
memory
to
address up to 1
mi
Ilion words.
When
the
memory system comprises memory units of different sizes,
some precautions are necessary
to
prevent false address recognition
as well as to prevent gaps in
the
memory range.
1.
If
all memory units have sizes
that
are
powers of two, they
can
a II be di fferent; they must , however, be assi gned in order of
decreasing
size
in the address continuum.
For
instance, three memory units can be used
in
this manner:
Memory Unit
No.
Size
Address Range
--
1
64K
words
o
to
64K
word~
2
32K words 64
to
96K words
3
16K
words
96
to
112K
words
2.
If
a memory unit has a
size
that
is not a power of two,
it
must
be situated in a memory system that satisfies the following
rules:
a.
All other memory units must have sizes
that
are
a power
of two.
b. The starting address of the
non-power-of-two
unit must be
a multiple of
the'next
power of two above
the
size
of
that
unit.
c.
The memory unit whose
size
is not a power of two must be
at
the
upper end of
the
address range.
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