A computing system includes: an inter-device interface configured to receive a receiver signal for representing a serving signal; a communication unit, coupled to the inter-device interface, configured to: calculate a decoding result based on decoding the receiver signal, generate a parity portion adjustment for adjusting the decoding result, generate a systematic portion adjustment for adjusting the decoding result, and apply the parity portion adjustment and the systematic portion adjustment to the decoding result for determining the serving signal from the receiver signal.