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SECTION I
INTRODUCTION
The Model 120, a solid- state, high- speed computer of the Honeywell Series 200 Data
Processing System, is oriented toward business data processing applications.
Besides func-
tioning as an independent data processor, the Model 120 can also be used effectively as an
input/ output processor for larger computers.
The basic system consists of a central processor to which a high-speed printer, a card
reader, and a card punch can be connected.
Since one of the most significant features of the
Model 120 is its high degree of internal modularity, a varied complement of peripheral equip-
ment may be added to the basic system configuration to meet growing data processing require-
ments.
This capability enables the Model 120 to satisfy the input/ output requirements of
virtually any computer application.
The Model 120 main memory is a coincident-current memory consisting of high-speed
magnetic cores which are randomly addressed through a binary addressing system.
This
addressing system greatly simplifies the modular expansion of memory because it eliminates
the need for complex machine-language coding schemes to represent addresses in expanded
memory configurations.
The basic memory complement is 2,048 character locations, which
may be expanded in modular increments to 32,768 locations.
The first memory module added
must be 2,048 characters, after which up to seven modules of 4,096 characters each may be
added.
The memory cycle time of the Model 120 (i. e., the time required to read and restore
one character in main memory) is three microseconds.
Another important feature of the Model 120 is the linear- select control memory which,
like the main memory, is a magnetic-core storage unit.
The control memory consists of 16
individually addressable registers, each of which is capable of storing one main memory
address.
Its primary function is to provide storage for the operational registers of the central
processor and the various activated peripheral devices.
More specifically, it retains the ad-
dresses that describe the various transfers of information to and from main memory, plus the
addresses of program instructions and operands.
The central processor traffic control unit in the Model 120 consists of three read/write
channels, which makes possible the performance of peripheral operations simultaneously with
computing.
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