Cisco 12404 Installation And Configuration Manual page 39

Chapter 1 Product Overview
SDRAM
Caution
DIMM
SRAM
NVRAM
Caution
OL-11636-01
The SDRAM on the PRP stores routing tables, protocols, and network accounting
applications. It also runs the Cisco IOS software. The default PRP SDRAM
configuration is 512 megabytes (MB) of SDRAM, which you can increase up to
1 GB maximum, through DIMM upgrades. You cannot mix memory sizes. If two
DIMMs are installed, they must be the same memory size.
We recommends that you use only Cisco approved memory. To prevent memory
problems, SDRAM DIMMs must be +3.3VDC, PC133-compliant devices. Do not
attempt to install other devices in the DIMM sockets.
The Dual In-line Memory Module (DIMM) with 168 pins is a small circuit board
that holds memory chips and doubles the number of circuit paths to and from a
module by using independent pins on each side of the edge connector. You can
install DIMM memory modules one at a time.
The principle function of SRAM is to act as a staging area for routing table update
information to and from the line cards. SRAM also provides secondary CPU
cache memory. The standard PRP configuration is 2 MB. SRAM cannot be
upgraded or configured.
Non-Volatile Random Access Memory (NVRAM) cannot be upgraded or
configured. The system configuration, software configuration register settings,
and environmental monitoring logs are contained in the 2 MB NVRAM, which is
backed up with built-in lithium batteries that retain the contents for a minimum of
five years.
Before you replace the RP in the system, back up the running configuration to a
Trivial File Transfer Protocol (TFTP) file server or an installed Flash memory
card so you can retrieve it later.
Cisco 12404 Internet Router Installation and Configuration Guide
Route Processors
1-15