XtratuM's web site

XtratuM is a nanokernel that goes beyond the classical ideas of the nanokernel.

The lower level layer that directly deals with hardware is commonly called HAL (Hardware Access Layer). The most real time kernels (MaRTE OS, ORK, S.Ha.R.K., RTLinux/GPL, etc.) access the hardware in a similar way.

There are two hardware devices that directly affect the real-time capabilities of the RTOS: interrupts and timers. Special care has to be taken to program and manage interrupts in order to achieve a low latency handling. There are many harware devices that provide timers facilities (PIT, APIC, RTC, special IO boards). Handling these devices is not always easy to program since some of them are not present (or are hard to discover) in some boards.

XtratuM is a thin layer of software that provides a simple and convenient API to access interrupt mechanims and timer devices. XtratuM has been optimised to meet real time requirements.

Although XtratuM API can be used directly to implement an application, its has been designed to provide support to the guest operating system. Its API is intentionally small and simple.

Benefits of using XtratuM:

• Operating system developers have not to deal with the complexities of interrupts and timer hardware. XtratuM developers have allocated a lot of time and resources to achieve the maximum performance of the existing hardware.
• Porting of the guest RTOS to a new processor, supported by XtratuM, is almost immediate. The hardest part of a porting is to set up the boot to run the hello world program. XtratuM will give a bootable platform ready to run code and more.
• A version of XtratuM supports multiple RTOS by sharing the hardware among them. Interrupts are delivered to the RTOS in daisy-chain fashion. An optional facility of this version will be the memory protection of the RTOS. In this sense, XtratuM is quite similar to ADEOS, but XtratuM API and functionality is much more simple.
• One version of XtratuM has been designed to take advantage of running Linux jointly with the RTOS, that is, it is possible to execute concurrently the guest RTOS and Linux. In this version, Linux is executed in background. This mechanism provides a convenient framework to develop your RTOS, your RTOS is loaded as any other Linux kernel module and programming error (exceptions) are intercepted and reported by XtratuM.

All versions of XtratuM have the same API, so once you port (or develop) your RTOS to XtratuM you can get all these benefits just recompiling your code.

It is important to point out that XtratuM does not virtualise the processor or the architecture as Bochs or Vmware® does. The operating system has to be XtratuM aware.