Electrical computers and digital data processing systems: input/ – Input/output data processing – Direct memory accessing
Reexamination Certificate
2007-01-10
2009-11-17
Kindred, Alford W (Department: 2181)
Electrical computers and digital data processing systems: input/
Input/output data processing
Direct memory accessing
C712S207000
Reexamination Certificate
active
07620749
ABSTRACT:
A DMA device prefetches descriptors into a descriptor prefetch buffer. The size of descriptor prefetch buffer holds an appropriate number of descriptors for a given latency environment. To support a linked list of descriptors, the DMA engine prefetches descriptors based on the assumption that they are sequential in memory and discards any descriptors that are found to violate this assumption. The DMA engine seeks to keep the descriptor prefetch buffer full by requesting multiple descriptors per transaction whenever possible. The bus engine fetches these descriptors from system memory and writes them to the prefetch buffer. The DMA engine may also use an aggressive prefetch where the bus engine requests the maximum number of descriptors that the buffer will support whenever there is any space in the descriptor prefetch buffer. The DMA device discards any remaining descriptors that cannot be stored.
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Biran Giora
De la Torre Luis E.
Drerup Bernard C.
Gupta Jyoti
Nicholas Richard
International Business Machines - Corporation
Kindred Alford W
Talpis Matthew B.
Tkacs Stephen R.
Unelus Ernest
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