Method and apparatus to enable DRAM to support low-latency access via vertical caching

• Main Authors: Jain, Sanjeev, Rosenbluth, Mark B, Adiletta, Matthew, Wolrich, Gilbert
• Format: Patent
• Language: English
• Published: 29.01.2008

Method and apparatus to enable slower memory, such as dynamic random access memory (DRAM)-based memory, to support low-latency access using vertical caching. Related function metadata used for packet-processing functions, including metering and flow statistics, is stored in an external DRAM-based store. In one embodiment, the DRAM comprises double data-rate (DDR) DRAM. A network processor architecture is disclosed including a DDR assist with data cache coupled to a DRAM controller. The architecture further includes multiple compute engines used to execute various packet-processing functions. One such function is a DDR assist function that is used to pre-fetch a set of function metadata for a current packet and store the function metadata in the data cache. Subsequently, one or more packet-processing functions may operate on the function metadata by accessing it from the cache. After the functions are completed, the function metadata are written back to the DRAM-based store. The scheme provides similar performance to SRAM-based schemes, but uses much cheaper DRAM-type memory.