Flash
It is also permanent storage device. It stores the compressed form of Cisco IOS software image and the NVRAM data.
Device structure
One flash socket
Support 80 pin flash SIMMs
Dual bank
Note: 16MB flash presents in built in mode in 2600XM series motherboard.
NVRAM
It is an EPROM,it is used for writable permanent storage device of the startup configuration. In Flash device, NVRAM data is stored where the boot code is loaded.
There are two type of dynamic memory
1) DRAM
2) SDRAM
Two dual in line memory module sockets are available in cisco 2600 series. 100-pin DRAM can be fitted in each socket. For configure the DRAM as combine of shared memory , to use the iomem software command . It is used for data transmitted or received by WAN interface cards ,NM and public buffer which is allotted for the CPU.
The Cisco 2691 router contains two 168-pin DIMM sockets for SDRAM. 168 pin SDRAM can be fitted with each socket .if you assemble one DIMM, you must put it in slot 0
Memory structure overview is given above.
There are two types of memory buffer such as system buffer and interface buffer.
System Buffer
It is provided of process the packets and it is created by Cisco IOS.
Interface Buffer
Interface buffer is nothing but particle based. using particles for interfaces with maximum transmission unit for avoiding overhead. According to buffer size, it is short buffer size than system buffer.