RFiof: an RF approach to I/O-pin and memory controller scalability for off-chip memories

Abstract

Given the maintenance of Moore's law behavior, core count is expected to continue growing, which keeps demanding more memory bandwidth destined to feed them. Memory controller (MC) scalability is crucial to achieve these bandwidth needs, but constrained by I/O pin scaling. In this study, we introduce RFiof, a radio-frequency (RF) memory approach to address I/O pin constraints which restrict MC scalability in off-chip-memory systems, while keeping interconnection energy at lower levels. In this paper, we model, design, and demonstrate how RFiof achieves high MC I/O pin scalability for different memory technology generations, while evaluating its area and power/energy impact. By introducing the novel concept of RFpins -- to replace traditional MC I/O pins, and using RFMCs - MCs coupled to RF transmitters (TX)/receivers (RX), while employing a minimal RF-path between RFMC and ranks, we demonstrate that for a 32-out-of-order multicore configured with off-chip ranks with a 1:1 core-to-MC ratio, RFiof presents scalable 4 RFpins per RFMC -comparable to pin-scalable optical solutions - and is able to respectively improve bandwidth and performance by up to 7.2x and 8.6x, compared to the traditional baseline -- constrained to MC I/O pin counts. Furthermore, RFiof reduces about 65.6% of MC area usage, and 80% of memory path energy interconnection.