Xerox 4220/MRP - Manual (Page 81)

A. Performance enhancement
Adding memory
For the fax modem option to take advantage of RAM added to
your printer beyond the standard eight megabytes, a “Restore to
factory defaults” should be preformed at the printer after
additional RAM is installed. This is done by pressing the Reset/
R
and Pause/ P keys simultaneously at the printer control panel.
A maximum of 20 MB of memory may be installed in the printer.
When faxing and printing at the same time, or when sending and
receiving complex faxes, additional memory provides increased
performance.
Adding a hard disk
To ensure a maximum amount of space for PostScript-to-
PostScript file transmissions using the fax modem, a high-capacity
hard disk may be added to the printer.
Installing a hard disk in the printer also allows you to spool fax
jobs.
XEROX MRP FAMILY FAX MODEM FOR MS-DOS OPERATOR GUIDE A-1