Custom accelerators improve the energy efficiency, area efficiency, and performance of deep neural network (DNN) inference. This article presents a scalable DNN accelerator consisting of 36 chips connected in a mesh network on a multi-chip-module (MCM) using ground-referenced signaling (GRS). While previous accelerators fabricated on a single monolithic chip are optimal for specific network sizes, the proposed architecture enables flexible scaling for efficient inference on a wide range of DNNs, from mobile to data center domains. Communication energy is minimized with large on-chip distributed weight storage and a hierarchical network-on-chip and network-on-package, and inference energy is minimized through extensive data reuse. The 16-nm prototype achieves 1.29-TOPS/mm ² area efficiency, 0.11 pJ/op (9.5 TOPS/W) energy efficiency, 4.01-TOPS peak performance for a one-chip system, and 127.8 peak TOPS and 1903 images/s ResNet-50 batch-1 inference for a 36-chip system.