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Legacy Computer Replacement System (LCRS)

LCRS is a drop-in SEL/Gould/Encore host replacement solution that runs unmodified legacy code on COTS hardware/software, delivering 100% code compatibility and dramatically improved performance at a fraction of the cost and risk of traditional re-hosting.


Since the SelBUS architecture’s introduction in 1975, SEL/Gould/Encore/Compro customers have enjoyed a continuous technology migration path.  This philosophy has protected our customers’ significant application software investment—by far the most costly system element.  Compro’s Legacy Computer Replacement System (LCRS) continues this tradition—and protects your software investment—by painlessly ushering legacy customers into the "Commercial-Off-The-Shelf" (COTS) world.

LCRS is comprised of:

  1. COTS System Environment (Linux-based hardware/software)
  2. Compro’s Real-Time Environment (RTE)
  3. Compro’s LCRS software

Each element is further described below.

COTS System Environment

LCRS uses Commercial-Off-The-Shelf (COTS) AMD Opteron computer systems running the SuSE Linux distribution.  It fully supports most built-in I/O including:

Additional I/O controllers (multi-port serial, SCSI, Gould High Speed Device, etc.) are also supported.

While COTS offers wonderful performance and maintenance advantages, it also poses long-term supportability risks.  In response, Compro's LCRS has migrated from Alpha, SPARC, and Intel based products, demonstrating its portability and largely hardware-independent advantage.  Bottom line – LCRS can "future-proof" your application.

Real Time Environment

The Real Time Environment (RTE) is a Linux extension (hardware and software) that adds high-performance interrupt latency and determinism to COTS systems. 

RTE includes:

The legacy RTOM is a central component in virtually all legacy SEL/Gould/Encore host computers.  The PCI-RTOM is a plug-compatible replacement for the legacy RTOM.

A complete description of the RTE is provided here.

Compro LCRS Software

LCRS is simply an application that simulates legacy SEL/Gould/Encore hardware while retaining inherent system timing.  Regardless of the legacy software (MPX-32 operating system, modified OS, binary code, FORTRAN, etc.), if it ran on legacy hardware, it will run under LCRS.

LCRS will run existing binary code.  In situations where source code is lost or indecipherable, LCRS is the only available solution.

LCRS uses a simple Linux user-configurable data file to specify system characteristics at runtime.  Elements include memory size, simulated disk pathnames, device handlers and shared memory partition names permitting concurrent LCRS instances on multiple computers.

Because legacy code requires no modification, LCRS offers the best-value solution when it's time to replace outdated hardware.  Undeniably, re-writing application code for a new computer system represents enormous risk and cost.  LCRS eliminates these re-hosting downfalls entirely.

Input/Output Considerations

Most legacy systems connect with a variety of subsystems using I/O connections such as Ethernet, High Speed Device (HSD), Real Time Option Module (RTOM), Reflective Memory System (RMS), RS-232, etc.  LCRS addresses connectivity to these existing subsystems by offering PCI versions of the legacy controllers.

The LCRS design goal is to protect not only your software investment, but to retain, when desirable, existing I/O subsystems.  All the above-mentioned I/O methods can connect to an LCRS bulkhead—using existing I/O cables!  Your subsystems will "never know the difference" and will continue to function as always.

Standard legacy peripherals (disk drives, magnetic tape, printers) are easily replaced with compact, modern COTS devices that under-cost, outperform and outlast their legacy counterparts.  And again, they appear functionally identical to your legacy application.

Prevailing wisdom would assume that since LCRS is "simulating" (or some would say "emulating") hardware, performance must suffer.  Nothing could be further from the truth.  In documented benchmarks, a simulated RSX computer (Encore's fastest proprietary system) runs approximately 200% faster under LCRS.  Older systems (32/97, 32/67, 32/77) enjoy performance gains ranging from 250% to 1800%.

Although overall performance is dramatically improved, system timing remains intact.  This is because real time applications are frame-based, and rely upon a system clock (provided by the PCI Real Time Option Module), and still execute at the same frame rate.  However, tasks within the frame execute faster, leaving more "headroom" for additional frame tasks.

The following table summarizes LCRS features and benefits:



Executes unmodified legacy applications

Slashes host replacement costs

Uses COTS hardware and software

More maintainable and reliable

Plugs into existing subsystems

Reduces risk and speeds deployment

Retains legacy timing & improves performance

Assures compatibility and increases frame headroom

Additional Information

To download Compro's LCRS white paper, please click here.

Pricing Information

Pricing is dependent upon the current system configuration, and is available after a system requirement evaluation.  Please call or email Compro to arrange a no-obligation evaluation.


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