Cisco Gigabit Switch Router 12008 Installation And Configuration Manual page 61

Overview of the Cisco 12008
Note If a single DIMM module is installed, it must be placed in bank 1 (U15).
SDRAM
SDRAM stores routing tables, protocols, and network accounting applications, and runs the
Cisco IOS software. The default PRP configuration includes 512 MB of error checking and
correction (ECC) SDRAM. DIMM upgrades of 512 MB and 1 GB are available. You
cannot mix memory sizes. If two DIMMS are installed, they must be the same memory size.
Cisco Systems strongly recommends that you use only Cisco-approved memory.
Caution
To prevent memory problems, SDRAM DIMMs must be +3.3VDC, PC133-compliant
devices. Do not attempt to install other devices in the DIMM sockets.
SRAM
SRAM provides 2 MB of parity-protected, secondary CPU cache memory. Its principal
function is to act as a staging area for routing table updates and for information sent to and
received from line cards. SRAM is not user configurable and cannot be upgraded in the
field.
NVRAM
NVRAM provides 2 MB of memory for system configuration files, software configuration
register settings, and environmental monitoring logs. This information is backed up with
built-in lithium batteries that retain the contents for a minimum of 5 years. NVRAM is not
user configurable and cannot be upgraded in the field.
Flash Memory
Flash memory allows you to remotely load and store multiple Cisco IOS software and
microcode images. You can download a new image over the network or from a local server
and then add the new image to Flash memory or replace the existing files. You then can boot
the routers either manually or automatically from any of the stored images.
Product Overview 1-39