In many situations there are specialised computer systems, well into their middle age, that continue to perform critical if not vital tasks. These "Legacy Systems" are found in both defence and civil applications, and may well have been inherited by their current support staffs. The list of such systems is extensive and includes radar display and air traffic control, telecommunications, weather systems, flight simulation, airborne reconnaissance, industrial process control, seismic data acquisition, vehicle data acquisition and control, satellite download, and sonar/radar data logging. These disparate systems often share a common set of problems caused, in part, by their specialised nature:-

Non-portable Software

In many cases the operating system and applications software cannot easily be moved to a modern hardware platform. Its correct real-time operation is totally hardware dependent. Such dedicated safety critical software may have taken many years to develop and prove. The cost and time-scale to convert or re-engineer such software, and then test and approve operation on new hardware may be difficult to predict.

Hardware Obsolescence

On the other hand, the impact of hardware obsolescence on the operating cost, reliability, availability and maintainability of the legacy system may be unacceptable. In many cases the legacy electronics in the host processors may continue to meet reliability and performance targets. The more serious reliability problem often lies with the electromechanical peripherals, such as tape drives, printers, and significantly, with hard and floppy disk drives. In older systems, paper tape or punched card data entry may also be an issue. Obsolescent tape and disk drive products may set the speed limit in systems which experience a growth in required performance and will finally limit system availability as the spare part reserve becomes depleted and repair, if possible, is the only option.

Where data storage products are concerned, the rate of development is so fast that even new systems can fall rapidly into the legacy category within years or even months. For this reason the wise purchaser of new systems will concurrently procure critical lifetime spares.

Operating Environment

Legacy systems are often required to work in unique and difficult operating environments, where the cost and logistics of overall system replacement or upgrade can pose seemingly insurmountable problems. This can range from the need for continuous operation without down-time at remotely controlled sites to the harsh physical environments experienced by airborne or other mobile installations. The environment may also include non-standard data interfaces to the process, further increasing the cost of total system replacement.

Our Solution

In many cases it is possible to prolong legacy system life, and increase performance, by identifying and replacing the high-risk hardware elements. This can be done by emulating their function directly at product level, or by using modern equivalents and providing host compatible peripheral controllers.

Our family of hard disk or solid state based emulators; provide a general solution for disk drive replacement at product level. This is done without the need to make software or hardware changes to the host system and often has the effect of increasing system throughput, as emulated access (seek) time can be greatly reduced. Invariably the system reliability (MTBF) is improved far beyond the original equipment specification, as is the immunity to harsh environments. MTTR and security are also improved; error rates being eliminated by on-the-fly error correction and "perfect" media.

Ruggedised disk arrays (RAIDs or JBODs) may be used to emulate high performance, high capacity, airborne mission recorders. Large scale, wide bandwidth disk arrays may be used to replace ground or ship based data recording systems (Sonar or Radar track/display and data recorders) where previously tape arrays were used.

Where the emulation cannot be achieved at product or peripheral level, we will consider the design and supply of upgraded replacement host controllers to allow the connection of modern low-cost peripherals at legacy processor bus level. The cost of this approach varies greatly with the application.

Whichever approach is taken, the first step is to contact the Tiger product group at Reactive, providing as much information as possible about the application, the target product or subsystem, and the host interface to be emulated. We provide Emulation Questionnaires to assist with this process. In many cases a match will be found with a product from our range, or a small adjustment will allow compatibility to be achieved. In the worst case a feasibility study may be required, followed by the design and manufacture of a dedicated solution.

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