RISC System/6000: The UNIX Alternative

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The UNIX Alternative

by Teresa Elms

It's faster than a speeding bullet, more powerful than a locomotive, and it helps design things (such as airplanes) that leap tall buildings in a single bound. It's IBM's new RISC System/6000, and it's a super box. According to benchmarks conducted by IBM, the RS/6000 dramatically outperforms all leading competitors in the market for technical and numerically intensive computing. But many commercial midrange systems users--the primary market for the AS/400--also will find the UNIX-based RS/6000 a seductive alternative.

The RS/6000 Family: Architected for Power

The RS/6000 line consists of six system units in desktop, deskside, and rack-mounted configurations (Table 1). Single-user technical workstations are called POWERstations, while multi-user systems and systems that function as LAN servers are called POWERservers. Both names refer to IBM's new Performance Optimization With Enhanced RISC (POWER) architecture, which supplants the older RISC (Reduced Instruction Set Computer) architecture used in the IBM RT PC series.

The POWER architecture has a number of interesting features that amply justify the name. For example, the POWER RISC processor consists of three functional units: a branch unit (which is capable of processing two instructions in one instruction cycle), a fixed-point arithmetic unit, and a floating-point arithmetic unit. These functional units operate concurrently, permitting the RS/6000 to execute as many as four instructions during one instruction cycle. Cache memories for both instructions and data further improve performance. Using this processor design, the RS/6000 executes up to 150 million instructions per second (MIPS) during bursts of peak performance, and averages from 27.5 MIPS to 34.5 MIPS, depending on the CPU model. The processor is implemented in high-density CMOS (complementary metal-oxide semiconductor) technology that packages from 200,000 to more than 1 million circuits per chip.

The RS/6000 is a virtual memory system that supports single-level storage-- that is, applications on the system view memory and disk resources alike as one large region of main memory. Current models support up to 256 MB of real memory and 256 terabytes (TB) of virtual memory. But the 32-bit POWER architecture theoretically supports up to 4 GB of real memory and 4 pedabytes (PB)--or 4 million billion bytes--of virtual memory. (That's a lot of memory, but the AS/400 comes out ahead in this regard: today's 48- bit machines address 281 TB of virtual memory, and the AS/400 architecture provides for a 64-bit address that supports nearly 2 million pedabytes of virtual memory.) Memory on the RS/6000 is implemented in 1 megabit (Mb) DRAM (dynamic random access memory) technology today, but IBM is promising 4 Mb DRAM by the end of the year--at which time real memory capacity will double to 512 MB.

The I/O architecture of the RS/6000 bears some similarity to that of the AS/400, in that distributed I/O processors offload the main processor and thereby improve throughput. In particular, a variety of dedicated graphics processors support everything from simple 2D graphics to 3D wire modeling to advanced 3D solid modeling in real time. But in contrast to the AS/400, which relies on proprietary bus technology, the RS/6000 I/O bus supports IBM's Micro Channel Architecture (MCA). This strategy lets the RS/6000 incorporate off-the-shelf I/O adapter cards from the PS/2. And in the RS/6000, the MCA bus delivers screaming performance, with a data transfer rate of 40 MB per second. (Compare that to the AS/400 I/O bus, which transfers data at the more pedestrian 5 MB per second.)

Thanks to support for MCA and for the Small Computer Systems Interface (SCSI) standard, the RS/6000 offers a variety of I/O options too numerous to detail. Of these, the secondary storage options of the system may be the most interesting. The RS/6000 supports 5.25-inch and 3.5-inch, high- speed, high-density magnetic disk drives for total internal storage capacities up to 12 GB. One option is a removable hard disk drive that allows confidential information to be physically removed and locked away when the system is not in use. Another option is in-board CD-ROM optical disk storage. All RS/6000 documentation is available on CD-ROM disks.

There's more. In a statement of direction issued at the time of announcement, IBM promised a serial fiber-optic channel for the RS/6000. That super-speed channel will support inter-processor communications as well as direct attachment to high-bandwidth I/O devices. Deskside and rack-mounted RS/6000 units (but not the desktop models) already incorporate hardware provisions for the upgrade. In addition, IBM promised an I/O adapter card to support the Fiber Distributed Data Interface (FDDI) standard. This adapter will allow the RS/6000 to attach directly to a 100 Mbps optical LAN.

The UNIX Alternative

The RS/6000 operates under AIX Version 3, IBM's extended version of the UNIX operating system. UNIX is attractive to many users because it offers a wide variety of applications software and because its open architecture allows applications to move readily--at least in theory--from one vendor's platform to that of another vendor. Significant variations in the UNIX standard make the latter ideal more difficult to achieve than it should be. But AIX Version 3 offers a partial solution: it is compatible with most of the major UNIX standards, including AT&T UNIX System V, the IEEE 1003.1 (1988) standard for a Portable Operating System for Computer Environments (POSIX), and Berkeley Software Distribution 4.3 UNIX. It runs the popular C, Bourne, and Korn "shell" environments. It is also source-code- compatible with the AIX/RT application programming interfaces. IBM plans to add compatibility with the X/Open Common Applications Environment (CAE) in the future.

Whole-hearted support for UNIX has been long in coming from IBM. Big Blue traditionally prefers proprietary systems like OS/400--which ironically is becoming more and more of a closed system while AIX embraces ever more open standards. But public resentment of such power plays by vendors in the past has created a market for open systems that is too big today to ignore.

"We are very, very serious about UNIX," notes Terry Lautenbach, IBM senior vice-president and general manager of IBM United States. IBM estimates that UNIX-based computer systems generate $25 billion in annual revenues worldwide, and that market is growing at 30% per year.

IBM may be more serious about UNIX than it is about its flagship commercial midrange processor, the AS/400. Virtually every advanced technology feature promised to AS/400 users "someday" is available on the RS/6000 today.

Have you been waiting for intelligent workstations to support a powerful windowing environment for AS/400 processing? The RS/6000 offers a choice of two host-based windowing environments today. AIXWindows Environment /6000 is a graphical user interface and toolkit based on the Open Systems Foundation (OSF) Motif standard; it runs on multiuser RS/6000 POWERservers and presents an interface similar in look and feel to the SAA Presentation Manager. AIX NeXTStep Environment/6000 provides an object-oriented, graphical user interface and development platform compatible with Steve Jobs' NeXT computer; it runs on single-user POWERstations. Both AIXWindows and NeXTStep support a graphically rich style of user interaction known (facetiously) as the WIMP interface--for Windows, Icons, Mice, and Pull- down menus. In addition, an intelligent X-Windows workstation, the Xstation 120, allows users to access multiple host applications concurrently in a networked environment. The Xstation 120 can communicate with any host system that supports the X-Windows graphical interface standard. All three RS/6000 windowing environments support Display Postscript for superior font appearance.

Have you been waiting for IBM's Document Content Architecture (DCA) and shared folders to let you manage compound documents that contain elements of text, data, graphics, and image information--easily, smoothly, all at once? The RS/6000 today offers InfoExplorer, a hypertext database search and retrieval system that provides concurrent, on-line access to both text and graphics information. Using InfoExplorer, users can trace hypertext links to find associated text and image information, customize the presentation on the display, set bookmarks, annotate documents with private notes, view graphics with zoom/pan capabilities, and copy or print text and graphics information. The RS/6000 Hypertext Information Base is one database you might explore with InfoExplorer. The Hypertext Information Base resides on either magnetic disk or CD-ROM and contains the system documentation--with integrated text and graphics--for the RS/6000. The RS/6000 system software uses this information base independently of InfoExplorer to provide on-line help support to users.

Have you been waiting for modern programming languages that are functionally complete and that perform well? Have you been waiting for the developer's tools that go with them? The RS/6000 supports C, FORTRAN, Pascal, COBOL, Ada, and an assembler. (The latter is essential for systems programmers who need access to machine code in order to build fast, efficient, reusable tools). Programmer productivity aids include a powerful developers toolkit, a graphics interface toolkit, a mathematical functions library that optimizes performance in complex problems, and a raft of Computer Aided Software Engineering (CASE) products. (We're told that an independent developer, Software Ireland, is working on an RPG compiler as well.) To encourage software vendors to create applications for the RS/6000 platform, IBM has introduced a developer's program similar to that offered by Apple. Software vendors and academic researchers approved by IBM may purchase RS/6000 machines, peripherals, and associated software at half price. These products must be used for the creation or porting of application software and may not be resold.

Have you been waiting for powerful connectivity and cooperative processing in a heterogeneous, multi-vendor network? The RS/6000 supports asynchronous ASCII communications, Ethernet LAN connection, and the Token- Ring LAN. It also supports TCP/IP and the international OSI standards for data communications. The widely used Network File System (NFS) and Network Computing System (NCS) also appear on the RS/6000, where they support distributed database management and distributed computing in a network environment. A product called Viaduct also lets the RS/6000 access AS/400 databases on an interactive, peer-to-peer basis via APPC and SQL/400.

The list goes on. UNIX is not the perfect operating system. Ease of use in the raw UNIX product is non-existent; the system is a programmer's dream but an end-user's nightmare. Data management is primitive by the standards of more modern multi-user operating systems. Security is trivially easy to breach, as the rapid proliferation of the Morris virus on Internet attests. OS/400 offers significant advantages in the areas of data management, transaction processing, security, and machine independence over traditional, bare bones UNIX. But in AIX Version 3, IBM extensions and add-on features address every one of these potential problems. The NeXTStep environment, in particular, provides both programmers and end-users with productive, friendly access to the capabilities of UNIX.

Peaceful Coexistence?

IBM now offers three multiuser computer lines in the $10,000-to-$1,500,000 price range that defines the "midrange" product class. Those computers are the 9370 (augmented in February with new, economical, low-end models), the AS/400 (also augmented in February at the low end), and the RS/6000. IBM claims that these system don't compete with each other, but in fact they compete head-to-head, offering different strengths (and weaknesses) that make each of them attractive in different niches of the market. Big Blue hopes to make that look less like competition by declaring a winner in advance within each market niche.

The first factor to assess in this niche-wise evaluation process is application software. For example, if you want to run existing System/370 application software on a smaller, less expensive machine, the new 9370 systems are your choice. (This prospect is distinctly uninteresting to System/36, System/38, and AS/400 users--not to mention first-time computer users not yet saddled with an application inventory.)

When deciding between the AS/400 and the RS/6000, things are a little more complex. According to Stephen B. Schwartz, general manager of the Application Business Systems unit that makes the AS/400, IBM spent millions of dollars on a market segmentation study that broke the midrange market into hundreds of extremely specialized application niches. The study found significant differences between tractor parts distributors and auto parts distributors, for example. Within each such narrowly defined niche, IBM looked for the best application software regardless of platform. That application software determines the system that the IBM representative will pitch to the prospective account.

However, more general criteria may help individual users evaluate which system is best for their environment. The AS/400 remains the platform of choice when:

Workload is transaction-oriented rather than compute-intensive

RPG or COBOL are the preferred development languages

Synchronous communications capabilities are primary

A large database must be maintained on a single CPU

Hundreds of terminals must be active concurrently

The application software of choice runs only on the AS/400

Loyalty to IBM is an important factor.

Conversely, the RS/6000 is a better choice when:

Workload is compute-intensive rather than transaction- oriented

C or FORTRAN are the preferreddevelopment languages

Asynchronous communications capabilities are primary

Smaller, distributed databases are maintained

Dozens of terminals must be active concurrently

The application of choice runsunder UNIX

Vendor independence is an important factor.

A final discriminating factor is price. Entry prices for the RS/6000 processors range from $7,475 to $88,695. These are some of the most competitive prices in the technical computing market, and they are significantly more competitive than prices for the AS/400. For further ease of customer entry, AIX Version 3 is sold on a tiered pricing basis that depends both on the processor model and on the number of users for which the system is configured. Prices range from $1,250 to $10,000 for the base AIX system.

Could IBM have done all this for the AS/400? It certainly seems so, but for whatever reason, it didn't happen that way. Meanwhile, the RS/6000 delivers--today--the tools that IBM's commercial midrange users are still waiting for. It does so on an IBM-engineered platform that boasts that famous IBM reliability and IBM support. That's the real lure of IBM's UNIX alternative.

 --------------------------------------------------------------------------- TABLE 1 RISC SYSTEM/6000 MODEL SPECIFICATIONS ______________________________________________________________________ Configuration: --Desktop-- --------Deskside--------- --Rack-- Model: 320 520 530 730 540 930 ______________________________________________________________________ Memory: Standard (MB) 8 8 16 16 64 16 Maximum (MB) 32 128 128 128 256 128 Internal DASD: Standard (MB) 120 355 355 355 640 670 Maximum (MB) 640 2,571 2,571 2,571 2,571 11,998 Expansion Slots 4 7 7 6 7 7 Parallel Ports 1 1 1 1 1 0 Serial Ports 2 2 2 2 2 2 LINPACK DP (MFLOPS) 7.4 7.4 10.9 10.9 13.0 10.9 Dhrystones (K/SEC) 48.3 48.3 60.7 60.7 72.2 60.7 MIPS 27.5 27.5 34.5 34.5 41.1 34.5 Availability 2Q90 2Q90 2Q90 4Q90 3Q90 3Q90 Entry Price $7,475 $21,475 $36,935 $67,190 $88,695 $59,535