Jan Altenberg, Linutronix GmbH

During the last few years, Linux has established itself as the fastest growing platform in the embedded sector. This arised from the fact that there is no other Operating System which supports such a big variety of different hardware. Also the ongoing rapid development of the Realtime Preemption Patch made Linux a perfect choice for controlling and automation tasks which require hard-realtime capabilities.

ARM CPUs are widely used in embedded designs. There is a huge variety of cheap ARM9 and powerful ARM11 and Cortex CPUs which are predestined for use in embedded realtime controllers (because of the low power consumption and the growing number of features).

This paper demonstrates the behavior of the Realtime Preemption Patch on different ARM based embedded designs. The specific measurement environments will be explained in detail and the basics on how to get the Realtime Preemption Patch running on a specific ARM platform (and the major pitfalls) will be shown. Also the differences among ARM9 / ARM11 and Cortex CPU designs and how those differences influence the realtime behavior will be examined. As a result, the paper provides a decision guide for choosing the best fitting ARM design for a Realtime Linux based embedded platform.