eXtended Memory Architecture

In the original, non-XM mode design of the INtime memory system the kernel manages a total of 4 GB of virtual memory for the entire kernel and all the applications on a node.

This is a limitation for some classes of applications, so a new feature, called XM ("eXtended Memory"), was introduced in INtime version 6.

An XM process ("eXtended Memory" process) has its own separate 4 GB of virtual memory space and does not use a VSEG allocated from the system virtual memory space. The top 256 MB of the virtual memory range for an XM process is reserved for use by the system but the remaining 3.75 GB may be used by the process.