RAM Configuration
Mernory configuration
and
addressing is set by
ten
address switches on
the
HP
98258A 4
Mbyte
RAM board.
These
switches
determine
the
top
address
of
a 4, 8,
or
16
Mbyte block
of
RAM.
When
the
Model 330 is configured, remember
the
4 Mbytes
of
processor
on-board
RAM
that
must
be
contiguous with
the
4
Mbyte
RAM controller
board
if
it's
installed.
One
or
two 4 Mbyte RAM controller
boards
are
supported
on Model 350 conlputers. Only one
is
supported
on Model 330s.
Setting Address Switches
RAM assemblies (either one of
the
three
combinations of
HP
98258A/B/C
RAM
boards
must
be configured on address boundaries equal
to
the
RAM on
the
assenlblies, In
other
words, 4
Mbyte assenlblies can only
be
addressed
to
every 4M addresses
starting
from
the
top
of RAM;
8 Mbyte 2-board assemblies
at
every 8M address;
16
Mbyte 2-board assemblies
at
every 16M
address.
Ten RAM configuration switches
(S31 (MSB)
through
S22 (LSB))
are
used on
the
HP
98258A
RAM Controller Board.
They
determine
the
addresses used on
the
assembly
and
are set
to
the
top address in
the
block of RAM
the
assembly will respond to.
Switches
are
set
to
one of
the
4 Mbyte
RA~1
blocks
starting
at
the
top
of RAM, address
FFFFFFFF.
Only
the
three
most significant digits (MSD) of hexadecimal addresses
are
affected.
As
the
first eight switches (S31
through
S24) represent
the
two MSDs,
the
last two switches
(S23,
S22) can only change
the
third
hexadecinlal MSD by 4M addresses;
the
lower two binary
positions of
the
third
hexadecimal digit
are
inlplied as
1.
Therefore, RAM
is
addressed in 4
Mbyte blocks.
Table 3-3 lists all possible configuration switch settings for a Model
350 computer. As
the
Model
330
is
limited
to
8 Mbytes of RAM, only
the
top
two switch settings are possible.
Table 3-3.
HP
98258A/B/C
RAM
Configuration
Decimal
3 Hex Switch
Address
MSDs Settings
4294967295
FFF
1111111111
4290772991
FFB
1111111110
4286578687
FF7
1111111101
4282384383
FF3
1111111100
4278190079
FEF
1111111011
4273995775
FEB
1111111010
4269801471
FE7
1111111001
4265607167
FE3
1111111000
Functional Description
91
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