RMX (operating System) - IRMX Variants

IRMX Variants

Several variations of iRMX have been developed since its original introduction on the Intel 8080: iRMX I, II and III, iRMX-86, iRMX-286, DOS-RMX, iRMX for Windows, and, most recently, INtime. While many of the original variants of iRMX are still in use, only iRMX III, iRMX for Windows, and INtime are currently supported for the development of new real-time applications. Each of these three supported variants of iRMX require an Intel 80386 equivalent or higher processor to run.

A significant architectural difference between the INtime RTOS and all other iRMX variants is the support for address segments (see x86 memory segmentation). The original 8086 family of processors relied heavily on segment registers to overcome limitations associated with addressing large amounts of memory via 16-bit registers. The iRMX operating system and the compilers developed for iRMX include features to exploit the segmented addressing features of the original x86 architecture. The INtime variant of iRMX does not include explicit support for segmentation, opting instead to support only the simpler and more common 32-bit flat addressing scheme.

Note: despite the fact that native processes written for INtime can only operate using unsegmented flat-mode addressing, it is possible to port and run some older iRMX applications that use segmented addressing to the INtime kernel.

When Intel introduced the Intel 80386 processor, in addition to expanding the iRMX RTOS to support 32-bit registers, iRMX III also included support for the four distinct protection rings (named rings 0 through 3) which describe the protected-mode mechanism of the Intel 32-bit architecture. In practice very few systems have ever used more than rings 0 and 3 to implement protection schemes.