You may have been using CDE, but the default on IRIX in the 1990s was Indigo Magic Desktop (later called IRIX Interactive Desktop), with SGI’s own port of Motif

You may have been using CDE, but the default on IRIX in the 1990s was Indigo Magic Desktop (later called IRIX Interactive Desktop), with SGI’s own port of Motif. This used the 4Dwm window manager, which had window decorations like those of mwm, but with window title bar labels in bold, italic type.