IBM System/370 145 Manual page 22

the Model 145, a monolithic storage array chip is approximately an
eighth of an inch square and contains a little more than 1400
components, or about 174 interconnected circuits. These circuits form
storage bits and support circuitry on the chip. In the Model 145, one
monolithic storage array chip contains 128 storage bits and their
associated decoding, addressing, and sensing circuitry_
As shown in Figure 10.05.2, two storage array chips are mounted on a
half-inch-square substrate, and a pair of substrates is packaged into a
storage array module. Each half-inch-square storage array module, which
contains 512 storage bits, is mounted on a s'torage array card, shown in
Figure 10.05.3. The card is about 3-1/2 by 4-3/4 inches and contains
12K (12,288) storage bits. Storage array ca:rds are placed in storage
array boards which are called basic storage modules (BSM's). In outward
appearance, therefore, monolithic storage resembles monolithic logic
circuitry.
The primary basic storage module of the Model 145, which contains 48K
bytes of storage (on 12K bit storage array cards) and its associated
circuitry, is shown in Figure 10.05.4. It is approximately 13-1/4
inches long. 5-1/2 inches deep, and
9
inches wide.
A
256K Model 145
contains six of these 48K-byte basic storage modules (256K of processor
storage and 32K of control storage). When more than 256K of processor
storage is installed, a main storage frame is required and 32K-byte
BSM's are used in the main storage frame. The storage array cards used
in a 32K-byte BSM contain 8K bits.
since power is required to maintain a one or zero state in a
monolithic storage bit, data is lost when power is turned off, and
monolithic storage is therefore said to
be
volatile. This is not true
of core storage, which retains a magnetized state when power is removed.
12
The following are the advantages of monolithic over core storage:
• Faster storage speeds can be obtained, first, because of the shorter
paths between storage circuitry and, second, because of the
nondestructive read-out capability of monolithic storage. Since
core storage read-out is destructive, a :regeneration cycle is
required after a read and is also used prior to a write. This type
of regeneration cycle is not required for monolithic storage.
• storage serviceability is enhanced because storage is implemented in
accessible, easily replaceable cards, each of which is a functional
storage component. Diagnostic routines can be written that need
only identify the failing storage card, which can be replaced in a
matter of minutes. Storage increments can also be field-installed
rapidly.
• Space requirements for system storage are reduced. Dense bit
packaging per chip is achieved by the use of monolithic technology
and by the fact that the regularity of a storage pattern lends
itself to such packaging. For example, ,256K of core storage on the
Model 40 requires almost twice the amoun't of space that 256K of
monolithic processor storage requires on the Model 145.
A
Guide to the IBM System/370 Model 145