An 8Tb/s 1pJ/b 0.8mm2/Tb/s QDR inductive-coupling interface between 65nm CMOS GPU and 0.1µm DRAM

Abstract

This paper presents an 8Tb/s 1pJ/b 0.8mm2/Tb/s quad data rate (QDR) inductive-coupling interface between 65nm CMOS GPU and 0.1µm DRAM. The interface consists of 1024-bit parallel inductive-coupling transceivers operating at 8Gb/s/link. In the DRAM transceiver, data are multiplexed and demultiplexed by using a quadrature clock and XOR operation. This circuit technique for QDR compensates for transistor performance gap between the GPU and the DRAM to achieve 8Gb/s bandwidth. The clock for data retiming is recovered from the received data by using an injection-lock VCO. Clock links and clock distribution circuits are not needed, resulting in small layout area of 0.8mm2/Tb/s. Frontend of the transceiver is implemented using NMOS CML circuits with adaptive bias control. The transceiver's sensitivity to PVT variations is small, enabling all the 1024 parallel transceivers to operate at BER≪10{−16}. It also reduces the design margin required of the transceiver, resulting in power reduction to 1pJ/b. Compared to the latest wired 40nm DRAM interface [1], the bandwidth is 32x higher, while the energy consumption is 1/8 and the layout area is 1/22.