Four Main Types of Cisco Memory in Cisco Hardware
Cisco is a large manufacturer of networking hardware, inter-network operating systems, network routers, switches and other similar devices. The actual design and layout of each product controls what types of Cisco memory can be used in the system device. This also influences what functions the memory serves in the system.
Cisco has four main types of memory in its hardware.
Dynamic Random Access Memory
Dynamic Random Access Memory (DRAM) is designed to work with computer systems that have two device requirements. One requirement would be the job that the processor memory performs. This is an operation that allows for exclusive memory access by the CPU, which it uses when executing software running on the Cisco IOS platform. Critical data such as configuration settings or routing tables are stored in the processor memory. The second requirement would be the function that the shared memory performs. This takes any and all data that comes in and out of the system and buffers it to what is called the packet memory. It is sent there before being transmitted over the network interface.
Erasable Programmable Read-Only Memory
Erasable Programmable Read-Only Memory (EPROM) is a memory system often unchangeable by consumers. When the system is being manufactured, it is one of the last stages left to complete. EPROM memory is installed with two components. One is the boot loader, which allows a system that may fail to find a bootable image in the flash memory and allow an alternate boot option. The second component is a ROM monitor, which comes with a user interface and options for troubleshooting any possible failures of the ROM chips.
Non-Volatile Random Access Memory
Non-Volatile Random Access Memory (NVRAM) performs the duty of storing configuration information used by Cisco IOS during booting and start-up. The NVRAM allows the functionality of the Cisco Software Configuration Register (SCR), which sole function is allow a device to be booted and chosen from the multiple IOS images stored in flash memory.
Flash memory has the widest variety of uses from all the Cisco memory types. The primary use for flash memory is to store bootable IOS images from which the system can define and use to start up. Most of the computers have installed the onboard flash memory the device uses to boot, but in some higher end systems, they can have the ability to boot up from a image stored on a removable flash memory card.