A Reconfigurable Heterogeneous Multimedia Processor for IC-Stacking on Si-Interposer

This paper presents a heterogeneous multimedia processor for embedded media applications such as image processing, vision, 3-D graphics and augmented reality (AR), assuming integrated circuit (IC)-stacking on Si-interposer. This processor embeds reconfigurable output drivers for external memory interface to increase memory bandwidth even in a mobile environment. The implemented output driver reconfigures its driving strength according to channel loss between the implemented processor and the memory, so it enables high-speed data communication while achieving $8\\times$ higher memory bandwidth compared to previous embedded media processors. The implemented processor includes three main programmable intellectual properties, mode-configurable vector processing units (MCVPUs), a unified filtering unit (UFU), and a unified shader. MCVPUs have 32 integer (16 bit) cores in order to support dual-mode operations between image-level processing and graphics processing. This mode-configuration enables a frame-level pipelining in AR application, so the proposed processor achieves $1.7\\times$ higher frame rate compared to the sequential AR processing. UFU supports 16 types of filtering operations only with a single instruction. Most image-level processing consists of various types of filtering operations, so UFU can improve media processing performance and energy-efficiency. UFU also supports texture filtering which is performance bottleneck of common graphics pipeline. A memory-access-efficient (off-chip memory) texturing algorithm named as an adaptive block selection is proposed to enhance texturing performance in 3-D graphics pipeline. UFU has two-level on-chip memory hierarchies, a 512B level-0 (L0) data buffer, and an 8 kB level-1 (L1) static random-access memory (SRAM) cache. The small-sized L0 data buffer limits direct references to the large-sized L1 SRAM cache to reduce energy consumed in on-chip memories. Unified shader consists of four homogeneous scalar processing elements (SPEs) for geometry operations in 3-D graphics. Each SPE has single-precision floating-point data-paths, since precision of geometry operations in 3-D graphics is important in today's handheld devices (high resolution). The proposed media processor is fabricated in 0.13 $\\mu{\\rm m}$ CMOS technology with 4 mm $\\times\\,$4 mm chip size, and dissipates 275 mW for full AR operation.