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

Image Number 6 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
Method of manufacturing crystalline silicon solar cells with improved surface passivation
Method and laser receiver for acoustically indicating a laser beam
Method for mapping resource units
System and method for multi-tiered meta-data caching and distribution in a clustered computer environment
Keypad assembly for electronic devices
Knee guard
  Randomly Featured Patents
Control of sidedraw on distillation column
Surface inspection apparatus and method
Recycling system for manipulation of intracellular NADH availability
Method for treating mixed wastewater from pharmaceutical chemical industry park
Invisible zipper
Delay locked loop (DLL) using an oscillator and a counter and a clock synchronizing method
Efficient memory controller
Parallel field liquid crystal display with substantially straight data and common electrodes inclined at an angle to a gate line
Semiconductor device having organically doped structure
Wheel spoke