In the classic movie, 2001: A Space Odyssey, the HAL 9000 supercomputer revolts against the crew members of the spaceship Discovery and is subsequently shut down to insure the continued survival of one of the astronauts. In one of the more dramatic moments, HAL tricks astronaut David Bowman into space and refuses to let him back in. Bowman, for his part, utters the immortal catch phrase, “Open the pod bay door, HAL!”

There is some controversy as to how HAL was named and whether the acronym is based on two or three words. Most sources state that HAL grew out of two words in the phrase heuristically programmed algorithmic computer: the H is said to come from heuristic, and the AL comes from algorithmic. Another story says that HAL is based on the IBM acronym, and that—if you compare the two words—you’ll see that each letter in HAL is strategically placed one alphabetic letter in front of IBM (H = I, A = B, L = M). In other words, HAL is always one step ahead of IBM. It’s unclear whether the IBM story has any credence, but it is fun to speculate about.

Given these stories, it’s interesting to note that HAL is also the acronym for the Microsoft Windows NT Hardware Abstraction Layer. Microsoft’s HAL is a thin layer of software provided by hardware manufacturers—not Microsoft—to hide, or abstract, hardware differences and dependencies from the higher levels of the NT operating system. With manufacturer-provided HAL routines and NT device drivers, different types of hardware (including processors and other hardware devices) all look alike to the operating system, removing the need to tailor Windows NT to the hardware with which it communicates.

After the HAL routines are in place, Windows NT accesses those routines through the use of APIs so that NT does not make any direct calls to the processor. HAL routines are called from both the base NT operating system (including the NT kernel) and from Windows NT device drivers. Because the HAL code is changeable from computer to

computer, Windows NT is essentially a portable operating system that can be run on any computer as long as that computer’s manufacturer has supplied the appropriate HAL routines.

The AS/400, on the other hand, also boasts of a processor-independent implementation through its Technology Independent Machine Interface (TIMI). Like HAL, TIMI enables OS/400 to be portable from processor to processor. It was TIMI that allowed OS/400 to move from CISC-based AS/400s to the faster PowerPC RISC-based systems without inflicting major trauma on their customers. All the advantages Microsoft offers with the HAL architecture are also available with TIMI, and IBM expects to press its TIMI advantage in the future as it upgrades the AS/400 to post-RISC technologies that may include 96- and 128-bit processors.

However, there is a big difference between TIMI and HAL. With the proper HAL installed, you can theoretically port Windows NT to any processor platform. While TIMI also allows the AS/400 to be processor-independent, IBM does not allow OS/400 to be ported to another platform. As opposed to Microsoft, IBM is a software and a hardware company. It has as much financial interest in the hardware and peripherals running OS/400 as it does in OS/400 itself. As a business decision, TIMI is used to upgrade AS/400 hardware according to IBM specifications, not to port OS/400 to other non-IBM platforms. OS/400 is still officially married to the AS/400’s physical architecture, and, for business reasons, it is not platform independent in the same way as Microsoft’s HAL.

So, given the different approach each company takes, which will become more popular in the marketplace?

Microsoft’s HAL architecture has the capability to run on a number of different systems from Intel to Digital Equipment Corporation (DEC) Alpha to IBM IPCS, and—when new systems, are released—it may also run on those systems provided a corresponding HAL is also released. Architecturally and businesswise, HAL is poised to move with the marketplace, quickly reconfiguring itself to take advantage of new processing developments. And—because it’s the manufacturer, not Microsoft, who is responsible for creating the HAL—routines should reach the marketplace faster because of the vendor’s financial interest in porting its products to NT.

IBM’s AS/400 has already shown the capability to grow with processor changes, but all changes are IBM-directed. In electing to use OS/400 for your business needs, you are also electing to use a predefined set of AS/400 hardware that, traditionally, has grown with the system (i.e., from the S/38 to AS/400 CISC machines to RISC-based computers). With IBM, you are buying into a total system—OS and hardware. IBM supports you as a total system user, but your processor upgrade needs move at IBM speed.

Which is better? As Microsoft shrinks the gap between AS/400 stability and performance and as more NT applications become available, this could be a horse race, depending on existing situations. For existing AS/400 customers who don’t want to migrate to a new platform, IBM will continue to perform upgrades to its existing base and sell new customers who value the AS/400’s robustness and stability. However, for new customers who are price conscious, the ability to run Windows NT applications on multiple platforms (from reasonably inexpensive to higher end) may be too enticing to pass up. New business application users may not want to pay IBM prices for such basic commodities as hard drive space and RAM. The HAL interface may actually hasten the day when Microsoft owns a significant part of the midrange marketplace.

Of course, the marketplace will be the judge as to which strategy is better. It will be their decision whether Microsoft’s HAL can run fast enough to stay one step ahead of IBM.

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