Electrical computers and digital processing systems: memory – Storage accessing and control – Control technique
Reexamination Certificate
2005-05-17
2005-05-17
Vital, Pierre M. (Department: 2188)
Electrical computers and digital processing systems: memory
Storage accessing and control
Control technique
C711S151000, C710S112000, C710S244000
Reexamination Certificate
active
06895482
ABSTRACT:
An improved computer memory subsystem determines the most efficient memory command to execute. The physical location and any address dependency of each incoming memory command to a memory controller is ascertained and that information accompanies the command for categorization into types of command. For each type of memory command, there exists a command FIFO and associated logic in which a programmable number of the memory commands are selected for comparison with each other, with the memory command currently executing, and with the memory command previously chosen for execution. The memory command having the least memory cycle performance penalty is selected for execution unless that memory command has an address dependency. If more than one memory command of that type has the least memory cycle performance penalty, then the oldest is selected for execution. Memory commands of that type are selected for execution each subsequent cycle until a valid memory command of that type is no longer available, or until a predetermined number has been executed, or until a memory command of another type has higher priority. If an address dependency exists between memory commands of different types, then memory commands of the same type of the oldest memory command is executed to avoid deadlock.
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Blackmon Herman Lee
Drehmel Robert Allen
Haselhorst Kent Harold
Marcella James Anthony
International Business Machines - Corporation
Ojanen Karuna
Vital Pierre M.
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