The NCR Century 200 system establishes a flexible, economical base for expansion to provide the customer with a variety of processing and performance capabilities. The basic system consists of the following: processor with 32K memory, I/O writer, integrated COT (card or tape reader), integrated printer, and dual spindle disc unit with controller. The I/O section of the basic system consists of four common trunks (quadraplex) , with trunk 7 dedicated to the integrated printer and trunk 0 dedicated to the operator's console, the COT and the I/O writer.

The nominal data transfer rate of the common trunks is 120KB, with each trunk being able to accommodate 8 peripherals.

Extended Memory

Memory sizes can be extended in variable increments up to 5l2K, as the customer's needs dictate. Within the memory sizes listed below, memory may be increased, with the necessary processor modifications, on the customer's premises.

The following memory sizes are available with the NCR Century 200:

32,768 bytes             98,304 bytes           262,144 bytes

49,152 bytes             131,072 bytes           393,216 bytes

65,536 bytes             196,608 bytes          524,208 bytes

Extended Bandwidth

The trunk bandwidth may be extended by converting trunk 6, or trunks 5 and 6, into high-speed trunks. Conversion to high-speed trunks increases the trunk transfer rate and, therefore, the bandwidth of the entire system. High-speed peripherals, which are those that have a transfer rate above 120KB, must be connected to a high-speed trunk. The system I/O bandwidth is extended from 320KB without high-speed trunks, to 487KB with one high-speed trunk, to 909KB with two high-speed trunks.

Extended I/O Simultaneity

A quadraplex system may be converted to an octaplex system by adding four 8-position trunks to the system and converting trunks 5 and 6 to high-speed trunks. The installation of this option extends the I/O capacity from 4-way simultaneity to 8-way simultaneity. The optional trunks (trunks 1, 2, 3, and

4) have a data transfer rate of l20KB. Trunks 5 and 6 must be converted to high-speed trunks with the addition of the four optional trunks; consequently, the system I/O bandwidth is also extended.

Multiprogramming

Multiprogramming is the concurrent execution of two or more programs. Stored in memory, under the control of a supervisor program (executive), are several programs that share processor and I/O facilities. Memory protection is provided by the base address register (BAR) and the limiting address register (LAR). BAR/LAR register contents can be changed only by the executive, to protect the integrity of the memory-resident programs (partitions). Each partition has its own set of 63 index registers, so that each program may assume a starting address of zero. Multiprogramming software provides a method of relocating programs in memory by the direct intervention and control of the operator. This assures efficient utilization of the available memory. Any NCR Century 200 system may be modified to allow multiprogramming. Included in the multiprogramming option are a minimum of 64K memory, LOGIC and TABLE COMPARE commands, user/supervisor states of operation, BAR/LAR registers and LOAD BAR command, octaplex option, interval timer option, some additional functions by existing commands, additional control and compare logic functions, and additional console functions.

Peripheral Options

A great variety of printers and other peripherals are available on an optional basis.

The NCR 640-200, the integrated printer used in the basic NCR Century 200 configuration, may be substituted with an integrated 640-210 or 640-300 printer. If printing loads of the system so dictate, common trunk printers (with controllers) may be used in addition to or in place of the integrated printer. Printers vary according to character set (64 characters/single numeric or 52 characters/double numeric), print columns (132 or 160), and printing speeds (600/1200 lines per minute or 1500/3000 lines per minute).

Available with the 640-200 integrated printer is an optional SCRIBE/SPRINT type drum with 72 characters in the print set.

As a substitute for the NCR 655-201 disc unit and controller, the user may select the optional NCR 657-101/102 disc unit with controller, which not only increases the total storage capacity of the magnetic disc file, but also increases the transfer rate of the data being read from or written on the disc and, therefore, the entire system throughput.

Optional peripheral units are too numerous to mention in this publication since its primary purpose is the functional description of the NCR Century 200 processor.