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ARM Architecture

© 2002–2003 University of New South Wales
© 2004–2006 National ICT Australia
© 2006–2007 Open Kernel Labs
page maintained by:
Ben Leslie (benno@ok-labs.com)
Carl van Schaik (carl@ok-labs.com)

Supported Kernels

The L4Ka::Pistachio kernel offers support for the ARM v4/v5 architectures. This includes support for ARM Fast Address Space Switching (FASS) which dramatically improves context switching time.
See l4ka.org for more information about L4Ka::Pistachio.

The ARM port currently runs on the following platforms:

  • PLEB
    The University of New South Wales' embedded hardware
    * Supports both PLEB1 (SA1100) and PLEB2 (XScale PXA255)
  • TuxScreen - StrongARM based phone platform.
  • Intel's IDXP450 Xscale development platform (XScale IXP450).
  • Texas Instruments ARM Innovator platform - ARM920T.
Porting the ARM architecture to new platforms is fairly simple, the port to the TuxScreen was done in half a day :-)


Open Kernel Labs (OK) provides a comercial derivative of the L4Ka::Pistachio kernel for embedded systems called OKL4 and an operating system support layer, Iguana. It supports a variety of ARMv4, ARMv5 and ARMv6 processors and porting to other processors is possible in a short period of time.

This kernel has an optimized IPC path and extensions providing fast context switches. Benchmarks have measured 151 cycles each way on inter-address space IPC on a 400MHz Intel XScale PXA255. This gives a 0.38 microseconds IPC time between different address spaces.

OK also provides virtualized Linux and RTOS (eCos and other) support. Wombat, the Linux 2.6 verion on OKL4, has much better context switching performance than native Linux on ARM9 CPUs due to fast-context-switching support. Wombat is an OK-maintained port of Linux 2.6, which runs on this kernel.

A contribution to the L4 community from the UNSW/NICTA/OK teams.