Visual Image Processing RAM: Memory Architecture With 2-D Data Location Search and Data Consistency Management for a Multicore Object Recognition Processor

Abstract

Visual image processing random access memory (VIP-RAM) is proposed for a real-time multicore object recognition processor. It has two key features for the overall processor: 1) single cycle local maximum location search (LMLS) for fast key-point localization in object recognition, and 2) data consistency management (DCM) for producer-consumer data transactions among the processors. To achieve single cycle LMLS operation for a 3 x 3 window, the VIP-RAM adopts a hierarchical three-bank architecture that. finds the maximum of each row in each bank. first, then. finds the. final maximum of the window and its address in the top level. To this end, each memory bank embeds specialized logic blocks, such as three successive data read logic and bitwise competition logic comparator. With the single cycle LMLS operation, the key-point localization task is accelerated by 2.6 x with a 27% reduction of power. For the DCM function, the VIP-RAM includes a valid check unit (VCU) that automatically manages the validity of each 32-bit data. It dynamically updates/checks the validity of the shared data when the producer processor writes the data or the consumer processor reads data. With a customized single-ended memory cell and multibit-line selection logic, the VCU can provide a validity check not only for single data access, but also for multiple data accesses such as burst and LMLS operation. Eliminating data synchronization overhead with the DCM, the VIP-RAM reduces the amount of on-chip data transactions and execution time in producer-consumer data transactions by 22.6% and 15.4%, respectively. The overall object recognition processor that includes eight VIP-RAMs and ten processors is fabricated in 0.18 mu m complementary metal-oxide-semiconductor technology with the chip size of 7.7 mm x 5 mm. The VIP-RAM occupies a 1.09 mm x 0.83 mm die area and dissipates 113.2 mW when it performs the LMLS operation in every cycle at 200 MHz frequency and 1.8-V supply.