Real Time Linux is rapidly finding application in several embedded systems because it is scalable, customizable and has a good development environment. However, problems arise on systems with low memory, and on systems that require to be booted fast. Linux is not optimized to boot fast, and requires at least 4MBytes of RAM.

This paper presents an embedded application: a Remote Terminal Unit (RTU), used in a Supervisory Control and Data Acquisition System (SCADA) to monitor and control critical process control plants. The RTU is based on Intels' 80486 microprocessor and has 2 MBytes of SRAM and 2MBytes of Flash memory. Besides this, the application requires the system to be booted in under one second.

FSMLabs' RTLinux was tuned to run on this system. This paper discusses two aspects of the tuning. First, the embedding of RTLinux on this low memory system. Second, the modifications made to reduce the boot time of the system.

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