Resources Contact Us Home
Multi-processor DRAM controller that prioritizes row-miss requests to stale banks

Image Number 2 for United States Patent #5745913.

Memory requests from multiple processors are re-ordered to maximize DRAM row hits and minimize row misses. Requests are loaded into a request queue and simultaneously decoded to determine the DRAM bank of the request. The last row address of the decoded DRAM bank is compared to the row address of the new request and a row-hit bit is set in the request queue if the row addresses match. The bank's state machine is consulted to determine if RAS is low or high, and a RAS-low bit in the request queue is set if RAS is low and the row still open. A row counter is reset for every new access but is incremented with a slow clock while the row is open but not being accessed. After a predetermined count, the row is considered "stale". A stale-row bit in the request queue is set if the decoded bank has a stale row. A request prioritizer reviews requests in the request queue and processes row-hit requests first, then row misses which are to a stale row. Lower in priority are row misses to non-stale rows which have been more recently accessed. Requests loaded into the request queue before the cache has determined if a cache hit has occurred are speculative requests and can open a new row when the old row is stale or closed.

  Recently Added Patents
Cryptography on a simplified elliptical curve
Virtual image display device and manufacturing method of virtual image display device
Method and apparatus for efficiently inserting fills in an integrated circuit layout
System and method for selecting a video encoding format based on feedback data
Cantilevered probe detector with piezoelectric element
Method for encoding signal, and method for decoding signal
Sabatier process and apparatus for controlling exothermic reaction
  Randomly Featured Patents
Synthesis of 2-(4-hydroxyphenoxy) alkanoic acid esters
Operating environment setting system and method for printer
Jet pipe
Method for selective herbicidal treatment of barley cultures
Juice extractor appliance and cutter disc therefor
Laser welding method
Process for preparing aldehydes from oxirane compounds
Personal defense device
Gloves, their manufacture and use