O-2A: Low overhead DNN compression with outlier-aware approximation

We present a low-latency DNN compression technique to reduce DRAM energy, significant in DNN inferences, namely Outlier-Aware Approximation (O-2A) coding. This technique compresses 8-bit integer, de-facto standard of DNN inferences, to 6-bit without degrading the accuracies of DNNs. The hardware for the O-2A coding can be easily embedded to DRAM controllers due to small overhead. In an Eyeriss platform, the O-2A coding improves both DRAM energy and system performance by 18~20%. The O-2A coding enables us to implement an error-correction scheme without additional parity overhead, opening the possibility of an approximate DRAM to simultaneously reduce DRAM accessing and refresh energy.