Command Vector Memory Systems: High Performance at Low Cost

The focus of this paper is on designing both a low cost and high performance, high bandwidth vector mem-ory system that takes advantage of modern commodity SDRAM memory chips. To successfully extract the full bandwidth from SDRAM parts, we propose a new mem-ory system organization based on sending commands to the memory system as opposed to sending individual ad-dresses. A command species, in a few bytes, a request for multiple independent memory words. A command is similar to a burst found in DRAM memories, but does not require the memory words to be consecutive. The command is sent to all sections of the memory array si-multaneously, thus not requiring a crossbar in the proper sense. Our simulations show that this command based memory system can improve performance over a tra-ditional SDRAM-based memory system by factors that range between 1.15 up to 1.54. Moreover, in many cases, the command memory system outperforms even the best SRAM memory system under consideration. Overall the command based memory system achieves similar or bet-ter results than a 10ns SRAM memory system (a) using fewer banks and (b) using memory devices that are be-tween 15 to 60 times cheaper. 1