Memory Systems - Cisco EF4116 Hardware Installation And Maintenance Manual

Memory Systems

Memory Systems
The Cisco 4000 series memory systems (see Figure 1-2) have the following functions:
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Figure 1-2
EPROM-based
Boot helper
ROM monitor
Cisco 4500, Cisco 4500-M, Cisco 4700, and Cisco 4700-M
EPROM-based
ROM monitor
1-4 Cisco 4000 Series Hardware Installation and Maintenance
Main memory—Stores the running configuration and routing tables. The
Cisco Internetwork Operating System (Cisco IOS) software executes from main memory.
Shared memory—Used for packet buffering by the router's network interfaces.
Nonvolatile memory—Stores the system configuration file and the virtual configuration register.
Flash memory—Stores the operating system software image. In the Cisco 4500-M, the Flash
memory also stores the boot helper software.
EPROM-based memory—In the Cisco 4000-M, EPROM-based memory stores the boot
helper—a subset of the Cisco IOS software—and the ROM monitor. In the Cisco 4500-M and
Cisco 4700, only the ROM monitor is EPROM-based. The boot helper image allows you to boot
the router when Flash memory does not contain a valid system image. In the Cisco 4500-M, the
ROM monitor allows you to boot a system image from Flash memory if a boot helper image is
not present in boot Flash memory.
The boot helper prompt is as follows:
router(boot)>
The ROM monitor prompt for the Cisco 4000-M is the greater than sign:
>
The Cisco 4500-M and Cisco 4700 ROM monitor prompt is as follows:
rommon 1 >
(See the appendix "Cisco 4000 Series Virtual Configuration Register," the appendix
"Cisco 4000-M ROM Monitor," and the appendix "Cisco 4500-M and Cisco 4700
ROM Monitor.")
Cisco 4000 Series Memory Systems and Software Images
Cisco 4000 and Cisco 4000-M
(xboot)
Flash-memory based
Cisco IOS
Flash-memory based
Boot helper
Cisco IOS
(xboot)