256/640K
System Board
The
256/640K
system board has either 256K, 512K
or
640K of
R/W
memory. The memory consists
of
dynamic 64K by 1 bit
chips in Banks 2 and 3 and dynamic 256K by 1 bit chips in Banks
oand 1 with
an
access time
of
200ns and a cycle time
of
345ns.
All
R/W
memory
is
parity-checked.
System Board
Minimum
Maximum
Memory
Pluggable
Pluggable
Storage
Storage
Modu
1
f?;S
(Banks
0-1)
(Banks
2-3)
64/256K
64K
256K
64K
by
2 Banks
2 Banks
1
bit
of
9
of
9
256/640K
256K
640K
256K
by
2 Banks 2 Banks
1
bit
of
9
of
9
and
64K
by
1
bit
ROM
The system board supports
both
read only memory
(ROM)
and
R/W
memory. It has space for 64K by 8
of
ROM
or
erasable
programmable read-only memory (EPROM). Two module
sockets are provided, each
of
which can accept a 32K
or
8K
device.
On
the
64/256K
system board, one socket has 32K by 8
bits
of
ROM, the other 8K by 8 bits.
On
the
256/640K
system
board,
both
sockets have 32K
by
8 bits
of
ROM
installed. This
ROM
contains the power-on self test,
I/O
drivers, dot patterns
for 128 characters in graphics mode, and a diskette bootstrap
loader. The
ROM
is
packaged in 28-pin modules and has
an
access time and a cycle time
of
250ns each.
System Board 1-13
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