Front end
From Computer History Wiki
The term front end usually refers to a small computer attached to a large one, which is used to offload input/output work from the larger machine. (Hence the alternative terms I/O processor and peripheral processor).
The advantage of offloading I/O activity to a separate computer is that the acivity involved in the overhead of processing an interrupt from a device (e.g. saving register contents) can be significant, so avoid bothering the main CPU with this work can produce significant efficiencies.
The front end machine can communicate with the main CPU in a number of ways. It may have direct access to the main memory used by the main CPU, a technique used in the PPUs of the CDC 6600, the DL10 of the PDP-10 family, etc.
