buses, the Amdahl 4745 offered a single bus which throughput capacity exceeded the aggregate throughput capacity of the two buses of the IBM 3745. The design of the Amdahl 4745 was such that the control program (NCP) could not tell whether it was operating in an IBM 3745 or in an Amdahl 4745 (or, for that matter, in an IBM 3725 or in an Amdahl 4725). Amdahl's logical and physical simulation of the IBM 3745 (IBM 3725) was that complete. Later, a very high-speed scanner was offered with the Amdahl 4745 (and also with the Amdahl 4725, for which IBM had no such corresponding 3725 offering) which offered increased redundancy over the IBM 3745 very high-speed scanner (1.544 Mbit/s, T1, or 2.048 Mbit/s, E1) by having the line switchable to a backup 4725/4745 under operator console control. Demise The 3705 was eventually replaced by the 3720 and 3725. The 3745 was similar but not entirely compatible. The 3705 was withdrawn from marketing in December 1985. Hardware maintenance service was withdrawn in January 1999. References 3704 and 3705 Principles of Operation ACF/NCP VERSION 3 FOR THE IBM 3705 AND 3725 COMMUNICATION CONTROLLERS Announcement Letter 283-396 dated November 15, 1983 3705 3705 3705 3705