HP 48g Graphing Calculator - Manual (Page 390)

Port 0
Port 0 is the only port memory available on all HP 48s. The memory
for port 0 is taken out of user memory—so objects stored in port 0
decrease the amount of user memory available. The size of port 0 is
dynamic—it grows and shrinks to accommodate its contents. This
diagram shows port 0 taking memory as necessary from user memory.
User J
memory "j
NUMI
’NUMI’RCL
0:NUM1 STO
NUMI
’NUM1’ PURGE
Port 0 0:NUM1 0:NUM1
If you don’t have or don’t want to use plug-in cards, you can use port
0 for storing backup objects and library objects.
28
Card Slot 1
The HP 48GX has two card slots. These card slots are not identical.
Card Slot 1 can accept a plug-in card no larger than 128 KBytes. Any
RAM memory on a card plugged into Card Slot 1 can be merged
with built-in user memory to expand the amount of active memory
available or it can remain as regular port memory. Card Slot 1 is
identical to the card slots available on its predecessor, the HP 48SX.
When port memory is used in Card Slot 1, it is designated as Port 1.
The cards plugged into Card Slot 1 can be either RAM or ROM.
Card Slot 2
Card Slot 2 can contain a plug-in card up to 4 MBytes in capacity.
(This translates into 4096 KBytes, of which only 3968 are accessible.)
RAM memory on a card plugged into Card Slot 2 cannot be merged
with built-in user memory. Instead, the port memory offered in Card
Slot 2 is divided into distinct ports of 128 KBytes each. Thus, a
1-MByte plug-in card offers Ports 2 through 9, each containing up to
128 KBytes of backup objects and libraries. A 4-MByte plug-in card
offers Ports 2 through 32. The cards plugged into Card Slot 2 can be
either RAM or ROM.
28-2 Libraries, Ports and Plug-In Cards