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Page 183 Table 4.1 Elements of the IBM 370 family (19701983). Machine Cycle Time (ns) Eff. Access Time (ns) Organization MIPS 370/138 2751430 715935 Serial 0.25 370/148 180225 540 Serial 0.50 370/158 115 207 Overlapped 1.00 370/168 80 192 Pipelined 2.50 3033 57 135 Pipelined 4.90 3083B 26 86 Uni-overlapped 5.60 3083J 26 86 Uni-pipelined 7.50 3081D 26 86 Dyadic-serial 10.20 3081K 26 86 Dyadic-pipelined 14.40 3081Q 26 86 Quadratic-pipelined 27.00 product line because the same circuit and packaging technology is used. The memory system is basically the same across the line, although there was some variation in cache sizes for individual processors. A family of computer systems is developed by altering the organization of the machine, going from well-mapped to pipelined machine organization, and accelerating different operations. Another strategy emerges; in addition to altering machine organization, IBM used multiprocessor structures for speedup. During the mid-1980s, IBM replaced the 3081X series with a 3090X series and correspondingly replaced the smaller family members with other offerings. For the high end, the cycle time was decreased to under 20ns, and vector facilities (VF) were introduced. Vector arithmetic facilities, discussed later in the text, provide the potential for a 23-times speedup on scientific and other suitable applications. For the '90s, IBM, through its S/390 series, offers both multiprocessing and vector facilities, plus faster cycle time and very large memory configurations (Table 4.2). In the early '80s, memory configurations were generally limited to 1664 MB; by the '90s, over 9 GB (1 GB control store and 8 GB expanded (slower) storage) were available. Finally, significantly expanded I/O capability was made available through the use of fiberoptic communication for I/O channel interconnection (ESCON, in IBM terms). The resulting S/390 family ranges in price from $70,000 to $22 million, weighs from 60 pounds to over a ton, and offers performance from under 10 MIPS to perhaps over 500 MIPS. In 1993, IBM once again revised the S/390 offerings, generally expanding functional capacity, improving performance, and improving price/performance. At the time of writing, the top-performing water-cooled model is the 982, and the top-performing air-cooled model is the 742. There are eight air-cooled models and ten water-cooled models; see Table 4.3. Notice the relatively predictable evolution of the processor capabilities and performance.
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