HP Color LaserJet 5500 Technical Reference Manual page 243

Resource Saving
Four conditions may cause the printer to reconfigure user
memory:
When the printer language changes, either implicitly or
explicitly by using the ENTER LANGUAGE command
(except when resource saving is enabled).
When the page protection setting changes, using the SET
or DEFAULT commands, or when the printer is reset
using the RESET or INITIALIZE commands or by using
the control panel.
When the resolution is changed using either the SET or
DEFAULT commands, or by using the control panel.
When changing the I/O buffering or resource saving
settings.
Reconfiguring printer memory erases all volatile
personality-specific resource information, including
downloaded fonts, PCL macros, and PostScript dictionaries
(however no I/O data is lost). Memory can be reconfigured
only when these conditions actually change the page
protection, resolution, or printer language status. For
example, if the resolution is at 600 dpi and an application
sends the @PJL SET RESOLUTION = 600 command,
memory is not reconfigured.
If resource saving is enabled, memory is reconfigured, but
all volatile personality-specific resource information (such
as fonts, macros, and PostScript dictionaries) are not lost
(see "Resource Saving" below). If resource saving is
disabled, these resources are erased.
Printers that support resource saving:
HP LaserJet 4 Plus, 4M Plus, 4V, 4MV, 4Si, 4SiMx, 4000
series, 5, 5M, 5P, 5MP, 6P, 6MP, 5Si, 5SiMx, 5Si Mopier
Resource saving is a feature that allows you to prevent loss
of permanent resources (such as fonts, macros, and
PostScript dictionaries) when the printer language, page
protection, or resolution status changes. You can use either
PJL or the control panel to configure resource saving on HP
Feature Support A-31