eXtended mode

All four text mode functions can be displayed simultaneously. This function enables channel, instrument, spectrum analyzer, pattern view and volume control function with a good preset in text mode. <x> will enable 132 column mode. <ALT>+<x> will switch to the default 80x25 mode with channel and instrument functions enabled.^4.11

Footnotes

... enabled.^4.11

If your VESA bios does not support 132 columns a 80x50 mode is used.