BUSES, THE SKELETON OF COMPUTER STRUCTURES 299

Thurber, Kenneth J., E. Douglas Jensen, Larry A. Jack, Larry L. Kinney, Peter C. Patton, and Lynn C. Anderson, "A systematic approach to the de sign of digital bussing structures," A FIPS Conference Proceedings (1972), Vol. 41, Part II, Fall Joint Computer Conference. [polling, arbitration methods, data synchronization; annotated bibliography with 93 entries]

The following four references cover the Unibus and some bus related aspects of the PDP 11 architecture.

Bartee, T., Digital Computer Fundamentals (Fourth Edition), Chapter 10, section 10.6, "Inter connecting System Components," and section 10.7, "Interfacing - Buses," pp. 455-470, McGraw-Hill (1977). [bus structures, including Unibus]

Cohen, J., Janson, P., McFarland, H., and Young, J. Jr., Data Processing System, U.S. patent 3,710,324 (9 Jan 1973). [PDP-11 system and Unibus]

Sutherland, Ivan E., and Carver A. Mead, "Microelectronics and Computer Science," Scientific American, Vol. 237, no. 3 (September 1977), pp. 210-228. [interconnections, Unibus]

Tanenbaum, Andrew S., Structured Computer Organization, Chapter 4, section 4.12, "The PDP 11/40 Microprogramming Level," pp. 196-204, Prentice-Hall (1976). [PDP-l 1/40 internal organization and Unibus operation]

Cohen, J., Janson, P., McFarland, H., and Young, J. Jr., Data Processing System, U.S. patent 3,815,099 (4 Jun 1974). [PDP-11 memory and peripherals/

The following references are the patents covering the Massbus design.

Jenkins S., Secondary Storage Facility for Data Processing System, U.S. patent 4,047,157 (6 Sept 1977). [Dual- Unibus RHJ I Massbus controller].

Levy, J., Jenkins, S., Ku, V., McLean, P., and Hastings, T., Drive Condition Detecting Circuit for Secondary Storage Facilities in Data Processing Systems, U.S. patent 3,911,400 (7 Oct 1975). [Massbus Attention Summary register]

Levy, J., Jenkins, S., and McLean, P., Secondary Storage Facility for Data Processing Systems, U.S. patent 3,999,163 (21 Dec 1976). [Massbus]

McLean, P., Jenkins, S., and Ku, V., Diagnostic Circuit for Data Processing System, U.S. patent 3,911,402 (7 Oct 1975). [Massbus peripheral maintenance register]

Sergeant, 0., Levy, J., Lignos, D., and Griggs, K., Drive for Connection to Multiple Controllers in a Digital Data Secondary Storage Facility, U.S. patent 4,007,448 (8 Feb 1977). [Dual-Massbus disk drive]

The Honeywell Megabus, described in the first reference below, was an independent development that has some ideas similar to the SBI and the Unibus. The second reference has a short description of the SBI. The third reference contains an intellectual precursor to the SBI, the "z-bus", which was implemented only in a simulation.

Conway, J.W., "Approach to Unified Bus Architecture Sidestepping Inherent Drawbacks," Computer Design (Jan 1977). [Honeywell Megabus]

Digital Equipment Corporation, VAX-11/780 Architecture Handbook, (1977), Chapter 2, section 2.2, "The Synchronous Backplane Interconnect," p. 23. [SBI]

Levy, John V., "Computing with Multiple Microprocessors, Report SLAC-161, Stanford Linear Accelerator Center, (Apr 1973); (Ph.D. thesis, Computer Science Department, Stanford University). [Z-machine and z-bus]

The next three references relate to a relatively new development, the contention-arbitrated serial bus. These are distributed-arbitration buses which have a single signal used for both arbitration and for data transfer. Further references can be found in these publications.

MacLaren, Don, Contention-arbitrated serial buses, Digital Equipment Corporation R&D Group internal memo (13 Sep 1977). [with 8 references]

Metcalfe, Robert M., Packet Communication, Report MAC TR-l 14, Massachusetts Institute of Technology Project MAC, (December 1973).

Metcalfe, Robert M. and David R. Boggs, "Ethernet: Distributed packet switching for local computer networks," report CSL 75-7, Xerox Palo Alto Research Center (November 1975).