Core Issue
The router may get stuck in a continuous loop, which may be due to a hardware issue. A continuous loop never lets you gain access to the router. The router continues to scroll error messages until it is powered off.
These symptoms may be observed on the console during the boot sequence:
Not enough memory in the system for IO memory
IO memory available 4110105 required 5242880 _> 2600
SYSTEM INIT: INSUFFICIENT MEMORY TO BOOT THE IMAGE!
Not enough memory in the system to run this image
Required pmem/iomem: 39435385/524288
*** System received a Software forced crash ***
Resolution
For a recovery procedure, refer to the Identifying a Continuous/Boot Loop Due to a Wrong Iomem Size section of Hardware Troubleshooting for the Cisco 3600 Series Router.