The Cisco IOS software executes from main memory. The boot helper image allows you to boot the router when Flash memory cards do not contain a valid system image. It also allows you to boot the router from a network server. Contains the ROM monitor, which permits you to boot the Cisco IOS image from a Flash memory card or Flash Disk if a boot helper image is not present in the Flash memory. Primary cache is closest to the processor core and has the fastest access.
Secondary cache has slower access than primary cache, but faster access than tertiary cache.
For example, a processor may have primary cache with separate instruction and data cache memory, but unified secondary cache. Cache memory physically located outside the processor is not integrated, and is sometimes referred to as external cache. These products are also available as DRAM upgrades. These products are also available as DRAM upgrades. These products are also available as DRAM upgrades.