Cisco 1603R User Manual page 12

Router Memory
Run-From-RAM Architecture
With RFR, the Cisco IOS image is stored in Flash memory (usually in compressed form),
but is loaded into RAM before being used to operate the router. The running software image
then resides in RAM, so a new software image can be downloaded and copied over the
software image stored in Flash memory.
In RFR routers, only a minimal boot-helper image is stored in the ROM for disaster
recovery. Initial loading of a software image into Flash memory is done over the console
port or the local Ethernet.
Because the Cisco IOS image is stored in compressed form in Flash memory and then
decompressed when loaded into RAM, the standard configuration for the RFR models
contains less Flash memory but more DRAM than the RFF models.
Table 1-3 is a summary comparison of these two memory architectures.
Table 1-3 Memory Architecture Comparison
Feature
Cisco IOS software
online download
Flash memory use
RAM use
DRAM capacity
1-8 Cisco 1600 Series Router Hardware Installation Guide
Run-From-Flash Routers
Yes, when using Dual Flash Bank memory Yes
• Stores uncompressed Cisco IOS
software image.
• The Flash PC card cannot be removed
when the router is operating.
• Packet memory
• Routing tables
• Dynamic memory used by Cisco IOS
software
• Standard: 2 MB onboard
• Maximum: 18 MB (with 16-MB
SIMM)
Run-From-RAM Routers
• Stores compressed Cisco IOS software
image.
• The Flash PC card can be removed after
the router has finished booting up and
has passed the power-on self-test.
• Packet memory
• Routing tables
• Dynamic memory used by Cisco IOS
software
• Running uncompressed Cisco IOS
software image
• Standard: 8 MB onboard
• Maximum: 24 MB (with 16-MB
SIMM)