+.B sgiSaverExtension\fP (class \fBBoolean\fP)
+There are a number of different X server extensions which can make
+xscreensaver's job easier. The next few resources specify whether these
+extensions should be utilized if they are available.
+
+This resource controls whether the SGI \fBSCREEN_SAVER\fP server extension
+will be used to decide whether the user is idle. This is the default
+if \fIxscreensaver\fP has been compiled with support for this
+extension (which is the default on SGI systems.). If it is available,
+the \fBSCREEN_SAVER\fP method is faster and more reliable than what will
+be done otherwise, so use it if you can. (This extension is only available
+on Silicon Graphics systems, unfortunately.)
+.TP 8
+.B mitSaverExtension\fP (class \fBBoolean\fP)
+This resource controls whether the \fBMIT\-SCREEN\-SAVER\fP server extension
+will be used to decide whether the user is idle. However, the default for
+this resource is \fIfalse\fP, because even if this extension is available,
+it is flaky (and it also makes the \fBfade\fP option not work properly.)
+Use of this extension is not recommended.
+.TP 8
+.B xidleExtension\fP (class \fBBoolean\fP)
+This resource controls whether the \fBXIDLE\fP server extension will be
+used to decide whether the user is idle. This is the default
+if \fIxscreensaver\fP has been compiled with support for this extension.
+(This extension is only available for X11R4 and X11R5 systems, unfortunately.)
+.TP 8
+.B procInterrupts\fP (class \fBBoolean\fP)
+This resource controls whether the \fB/proc/interrupts\fP file should be
+consulted to decide whether the user is idle. This is the default
+if \fIxscreensaver\fP has been compiled on a system which supports this
+mechanism (i.e., Linux systems.)
+
+The benefit to doing this is that \fIxscreensaver\fP can note that the user
+is active even when the X console is not the active one: if the user is
+typing in another virtual console, xscreensaver will notice that and will
+fail to activate. For example, if you're playing Quake in VGA-mode,
+xscreensaver won't wake up in the middle of your game and start competing
+for CPU.
+
+The drawback to doing this is that perhaps you \fIreally do\fP want idleness
+on the X console to cause the X display to lock, even if there is activity
+on other virtual consoles. If you want that, then set this option to False.
+(Or just lock the X console manually.)
+
+The default value for this resource is True, on systems where it works.
+.TP 8