Intelligent multiple stack management unit

A stack management unit for a processing system that manages multiple stacks and corresponding stack pointer data as a frame stack. The stack management unit utilizes a combination of a primary stack and a secondary stack as the frame stack. A background spill/fill detect unit determines when an overflow/underflow of the primary stack occurs. In response to an overflow/underflow condition, the background spill/fill detect unit controls the transfer of a frame portion between the primary stack and the secondary stack without halting the processing system.