Sweet New Mainframes

by Philip Smith III

August 6, 2006

IBM has always been a little unsure of how to deal with the low-end mainframe customer. From the days of machines such as the 4321/4331/4341 (.18 to .81 MIPS!), through the 9370 series (the up-to-3-MIPS “VAX killer” that didn’t), to the Personal/390 and Multiprise systems, low-end systems allowed IBM to “plant acorns” that would grow into mighty oaks—towering 3084s, 3090s, and 9672s—as a shop’s processing needs grew.

But, to some extent, these systems always seemed like afterthoughts: They would run mainframe applications, but some features available on “real” mainframes— multiprocessors, vector support, PR/SM Logical Partition (LPAR), et al.—weren’t available. The Multiprise 3000 offered the closest thing to the “real S/390 experience,” including LPARs and even Integrated Facility for Linux (IFL) engines, but was limited to two processors and was structurally different from its big brothers.

In 2002, the z800 (and, in 2004, the z890) were introduced as the replacement low-end machines. These were “real” mainframes in most senses, although the z800 was built by Hitachi (with some IBM parts) and was physically quite different from the z900. (The z890 was much closer to a z990, using the same processor “books,” but was air-cooled and limited to one book per system.)

With the advent of the z9-109 last July, the obvious next question was, “Where’s the z8?” In late April, IBM answered this question, and simultaneously replaced the unwieldy “z9- 109” name. The new, low-end systems are now “z9 Business Class” (“z9 BC,” machine type 2096), and the high-end systems are “z9 Enterprise Class” (“z9 EC,” still machine type 2094). The BC machines are “real” z9s: Like the z890, they use the same books as their larger cousins, and are air-cooled and limited to one book per system, but mechanically they’re otherwise almost identical.

Long-time IBM customers will find the new naming confusing, to say the least. IBM spent the better part of two decades pushing the term “enterprise” as a synonym for “business”; in addition, Basic Control mode (BCMODE) and Extended Control mode (ECMODE) were hardware-level bit settings on the Sytem/370 that controlled whether the machine operated as a System/360 (BCMODE) or System/370 (ECMODE), so “BC” and “EC” were already “taken” in graying mainframers’ minds.

Nevertheless, the z9 BC is a great step forward for mainframe customers. Code-named “Pollux” in development— from Greek “Polydeuces,” which means “very sweet”—these are sweet boxes indeed. The z9 BC ranges from 26 MIPS (for a detuned or “kneecapped” single processor) to something on the order of 3,000 MIPS for a full, seven-IFL machine. For those of us who “grew up” with systems below 1 MIPS, it’s nothing short of amazing to see that a full-speed z9 engine is north of 500 MIPS, making it faster than a five-way 9672 G5 machine—some pretty serious iron not too long ago!




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Philip Smith III