Chapter 38 The RW-400-a new polymorphic data system 479

A buffer module (BM) has the capability to control its acquisition and dissemination of information independently. The buffer provides a computer module with parallel data handling capability without complicating the problem processing program with the conventional intermixture of arithmetic and housekeeping instructions. Information previously generated by the processing program maybe appropriately disposed of within the system while processing continues. Data needed at a subsequent time in the processing may be retrieved from system storage in advance of need while processing progresses. The simultaneity of these operations not only materially increases over-all processing speed but also increases the practical utility of the less costly types of internal system storage such as a magnetic tape.

The computer (CM) or buffer (BM) modules, when acting in a controlling capacity, may initiate connection to an information storage or handling module during that part of the processing program when the two can work profitably in unison. The pair of modules thus interconnected neither affect nor are affected by other modules. Logical interlocks prevent unwanted cross talk among modules. An intermodule communication system lets controlling modules signal status or alert other such modules of their need to communicate. The decision by a module receiving an alert signal to permit interruption or to proceed is optional with that module. The optional interrupt feature is that needed to make the often-discussed but seldom-used program interrupt capability both useful and practical. Programs may thus permit interruptions only at convenient points in the processing sequence.

Modules may be assigned, under program control, to work together on a problem in proportion to its needs. As soon as a module's function is complete for a given problem, that module may be released for reassignment to some other task. The system is thus self-controlled to match processing capacity to each problem for the time necessary to do the job. Full system capacity may be brought to bear upon a very large problem when needed. This capacity may be apportioned among a number of smaller problems for simultaneous processing, program compilation, program checkout, module maintenance etc., when it is not needed for maximum system effort.

From the preceding system description, it is apparent that such equipment can be expanded from a modest initial installation into a very powerful and comprehensive information processing center as requirements warrant. More specific descriptions of principal system modules follow to give the reader a better feel for how this system might perform his information processing work.

The key to appreciative understanding of the power of the RW-400 lies in knowledge of intermodule connection. It is appropriate to describe the Central Exchange (CX) unit first, then follow with descriptions of the various modules.

The Central Exchange performs the vital function of interconnecting a pair of modules whenever requested to do so by either a computer or a buffer module. Since internal programmed control is only possible within a computer or a buffer module, one of the interconnected pair of modules must be either a computer or a buffer. The time in which any connection may be made or broken is about 65 microseconds. An exchange has basic capacity to connect any of 16 computer or buffer modules to any of 64 auxiliary function modules. There is nothing sacred about the number 16 since it is possible to extend the CX module's interconnection matrix through design modification when need arises. The CX is an expandable, program-controlled, electronic switching center capable of connecting or disconnecting any available pair of modules in roughly the time of one computer instruction execution. Figure 2 illustrates the permissible module interconnections within the Central Exchange.

Every intersection on the illustration represents a possible connection between modules. The "x-ed" intersections indicate typical connections in force at any point in time. The control logic of the CX module's connection table prevents more than one interconnection on any horizontal (controlling) or vertical (controlled) data path representation on the diagram. When connection is requested of the Central Exchange while one of the required modules is already carrying out a previous assignment, the requesting module can be programmed to sense this condition and wait until connection can be made without interference. Should waiting be undesirable, the requesting module can go on about its business and check back later to see when the desired connection can be made. There is an implication here, of course, that knowing the kind of a system he is dealing with, a programmer requests connections in advance of need whenever possible.

Provision for master-slave control is included via an Assignment Matrix established within the CX module by a computer module previously assigned to master status. Such a provision is necessary to preclude inadvertent connection requests from unchecked programs or malfunctioning control modules from affecting sets of modules simultaneously processing another problem. Connection requests are therefore essentially filtered through both an assignment and an interconnection validity matrix prior to being acted