DRAM or no-DRAM? Exploring linear solver architectures for image domain warping in 28 nm CMOS

Solving large optimization problems within the energy and cost budget of mobile SoCs in real-time is a challenging task and motivates the development of specialized hardware accelerators. We present an evaluation of different linear solvers suitable for least-squares problems emanating from image processing applications such as image domain warping. In particular, we estimate implementation costs in 28 nm CMOS technology, with focus on trading on-chip memory vs. off-chip (DRAM) bandwidth. Our assessment shows large differences in circuit area, throughput and energy consumption and aims at providing a recommendation for selecting a suitable architecture. Our results emphasize that DRAM-free accelerators are an attractive choice in terms of power consumption and overall system complexity, even though they require more logic silicon area when compared to accelerators that make use of external DRAM.