Abstract: A processing system isolates at a physically or logically separate memory region of a processing unit boot code that is received from an external boot source for programming a boot memory of the processing unit until after the boot code is validated to protect against buffer overruns that could compromise the processing system. The processing unit includes a secure buffer region of memory that is physically or logically isolated from the remainder of the processing unit for receiving boot code from an external boot source such as a personal computer (PC) such that any buffer overruns at the secure buffer simply overwrite data stored at the secure buffer, and do not affect data or instructions that are executing at the processing unit.