NT is real-time enough

We’re pleased Control Engineering continues to provide extensive coverage of PC-based control and its increasing popularity in automation applications.

In the April 1998 Control Engineering cover story, “PC-based Control Goes Real-Time” (p.54) the chart describes the Allen-Bradley open controller as software running the QNX operating system. The 1747-OC is in fact a Pentium-class personal computer with the ability to run multiple operating systems, including QNX, Microsoft Windows NT and others. Our soft control system is called SoftLogix, and it runs on native NT.

Secondly, the chart shows nearly half of the PC-based software offerings running native NT, yet you devote a disproportionate amount of time to real-time extensions. I think you’d do your readers a service by educating them about the fact that a vast majority of control applications being implemented today can be addressed with native NT unencumbered by the overhead and integration difficulties caused by real-time extensions.

NT with third party real-time extensions is essentially a proprietary operating system. If the goal of a PC-based control application is openness in terms of compatibility with other off-the-shelf Windows NT applications, it will not be inherently realized using third party extensions or RTOSs (real-time operating systems). Compatibility with future releases of NT will also be an issue.

Dave Johnson, vp controller business, Rockwell Automation, Mayfield Heights, O.

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