SECTION
10.
MEMORY
EXPANSION
CARDS
For
rnemory capabilities beyond 640 Kbyte,
HP
provides
two
memory expansion cards: the HP45973A 1/2 MB Memory
Expansion
Card
which contains 512 Kbytes
of
RAM, and
the
HP45974A 1
MB
Memory Expansion Card which supports 1024
Kbytes
of
RAM.
The memory expansion cards
use
256K x 1 dynamic memory
chips. The HP45973A 1/2 MB Memory Expansion Card contains
18
of
these RAM chips (including parity). The HP45974A 1 MB
Memory Expansion
Card
contains 36
of
these chips.
The memory expansion cards, must
be
inserted into
two
connector 16-bit
I/O
slots. Table 2.4 and table 2.5 give the pin
assignments
for
these connectors, and signal descriptions can
be
found
in
Section
2.
Parity and Refresh
Memory data
is
parity-checked when accessed. If a parity error
occurs, then a non-maskable interrupt (NMl) will
be
generated.
The NMI
can
be
cleared by writing
to
the memory expansion card
where the parity error occurred.
Refresh
of
dynamic memory
is
controlled on
the
main system
card. All memories using the --
REFRESH
line are refreshed at the
same time.
Memory
Expansion Cards 115
To Next Page
Loading...
Need help?
General
