Pipelined ALU for effective external memory access in FPGA

cache, external memory, FPGA, network monitoring

The external memories in digital design are closely related to high response time. The most common approach to mitigate latency is adding a caching mechanism into the memory subsystem. This solution might be sufficient in CPU architecture, where we can reschedule operations when a cache miss occurs. However, the FPGA architectures are usually accelerators with simple functionality, where it is not possible to postpone work. The cache miss often leads to whole pipeline stall or even to data loss. The architecture we present in this paper reduces this problem by aggregating arithmetic operations into the memory subsystem itself. Fast data processing is achieved because arithmetic operations working with external data are offloaded. Our architecture reaches a speed of 200 Mp/s (operations carried out). It is designed to be used in systems with link speeds of 100 Gb/s. It outperforms other implementations by a factor of at least 3. The additional benefit of our architecture is reducing the number of memory transactions by a factor of two on real-world datasets.