A system in which firmware residing in ROM may be upgraded without re-spinning silicon. A one-bit flag may be assigned for each patchable function representing a firmware upgrade. The first statement of each function may check its associated flag and determine if patch-code should be executed in place of the current function residing in ROM. If the flag is not set, the code may continue executing normally. If the flag is set, a function identifier may be placed into a global memory location, and an assembly language “jump” instruction may be executed, redirecting program control to a specified location in a volatile Scratch Read Only Memory (SROM) where the corresponding patched code may be stored. If more than one function is patched, the global identifier may be used to determine which patched function to execute. Using an assembly language “jump” instruction to redirect control results in the patched function's returning normally to its calling function once it has completed executing.