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Section 4

Network computers and computer networks

The RW-400 and the CDC 6600 are actually computer networks by our definition of a computer (Chap. 2, page 17). Yet because of the restrictions on the quantity and location of the components in these structures, we still consider them to be computers. On the other hand, two or more computers which are separated physically, yet connected constitute a computer network. Computer networks will appear in the future; it is important to understand the basis for them.

The RW-400-a new polymorphic data system

Chapter 38 presents the RW-400 (also called the AN/FSQ-27), a later version of the Ramo-Wooldridge RW-40 originally designed in 1959. The diagram (page 478) gives an indication of the relationship and names of the components. The PMS structure in Fig. 1 has more configuration details. At least six RW-400's were built for military command and control applications (although the number of computers of a type in existence has little to do with a machine's worth or ability).

The RW-40 ISP as given in Appendix 1 of Chap. 38 is a good example of a processor with a two-address instruction set. The ISP does not have index registers; it has a small state consisting of the accumulator (A), a limited extended accumulator (B), the program counter (P), and about 6 state bits. The Pc is limited by its ability to address directly only a 1,024-word Mp. The ISP is undoubtedly sufficient for solving the kinds of problems encountered by the computer and compares favorably with Whirlwind and the IBM 1800.

The RW-40 introduced multiple parts for reliability [Rothman, 1959]. Multiple Cs (or Mp-Pc and Mp-Pio) are provided for redundancy and capacity. However, the S('Central Exchange) which provides communication among the Cs may not have redundant parts. The multiple-computer concept can be viewed as the forerunner to our present computer networks, in which the central switching element is the Telephone Exchange. Over a longer time span, the RW-400 may be most significant as a pioneer. However, the whole system, with the exception of the small Mp's, is nicely designed. The problem of low speed T(typewriter, display)'s is handled well by transferring data from Mp-Pc to Ms(drum) for concurrent and independent T and P activity. Similar solutions are common for managing T activity by using an M, local to particular Ts, and local C's.

The structure should be compared with the CDC 6600 (Chap. 39) and the network examples in Chap. 40.

The CDC 6400, 6500, 6600, 6416, and 7600

The CDC 6600 development began in 1960, using high-speed transistors and discrete components of the second generation. The first 6600 was delivered in September, 1964. Subsequent compatible successors included the 6400, in April, 1966, which was implemented as a conventional Pc(a single shared arithmetic function unit instead of the 10 D's); the 6500 in October, 1967, which uses two 6400 Pc's; and the 6416 in 1966, which has only peripheral and control processors. The first 7600, which is nearly compatible, was delivered in 1969. The dual processor 6700, consisting of two 6600 Pc's was introduced in October, 1969. Subsequent modifications to the series in 1969 included the extension to 20 peripheral and control processors with 24 channels. CDC also marketed a 6400 with a smaller number of peripheral and control processors (e.g., 6415-7 with 7). Reducing the maximum PCP number to 7 also reduced the overall purchase cost by approximately $56,000 per processor.

The computer organization, technology, and construction are described in Chap. 39. ISP descriptions for both the Pc and Pc ('Peripheral and Control Processors/PCP) are given in Appendices 1 and 2 of Chap. 39.

To obtain the very high logic speeds, the components are placed close together. The logic cards use a cordwood-type construction. The logic is direct-coupled transistor logic, with 5 nanoseconds propagation time and a clock of 25 nanoseconds. The fundamental minor cycle is 100 nanoseconds and the major cycle is 1,000 nanoseconds, also the memory cycle time. Since the component density is high (about 500,000 transistors in the 6600), the logic is cooled by conduction to a plate with Freon circulating through it.

This series is interesting from many aspects. It has remained the fastest operational computer for many years. Its large


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