Patent
Scatter-gather in data processing system
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TLDR
In this article, a technique for transferring data between system memory which is arranged in pages and an attached storage system is described, which is useful with storage systems that do not support scatter-gather and comprises determining for each data transfer the identity of any requested sector which lies completely within a physical page; and for those sectors which lie within a physically-aligned pages, transferring the sectors directly between secondary storage and memory by DMA.Abstract:
Described is a technique which finds use in transferring data between system memory which is arranged in pages and an attached storage system. In such a paged memory, data which crosses pages having contiguous virtual addresses may map to data which crosses discontiguous physical pages. Scatter-gather is advantageously employed in such a system in order to achieve the transfer data directly between memory and storage usually by Direct Memory Access (DMA). A secondary storage device which supports scatter-gather usually includes hardware which will perform the necessary calculations to transfer the data to and from the correct locations in physical memory. The technique of the present invention is useful with storage systems that do not support scatter-gather and comprises determining for each data transfer the identity of any requested sector which lies completely within a physical page and the identity of any sector which crosses boundaries between discontiguous physical pages; and for those sectors which lie within a physical page, transferring the sectors directly between secondary storage and memory by DMA; and for those sectors which cross said boundaries, transferring each sector to either the memory or secondary storage via an intermediate buffer.read more
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References
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Patent
User scheduled direct memory access using virtual addresses
TL;DR: In this paper, an intelligent direct memory access (DMA) controller interprets user commands from a host system, translates virtual addresses from the user applications program to physical addresses, and retrieves blocks of data from the main system memory at the request of the user's code, rather than at the permission of the kernel code of the host system.
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System for DMA block data transfer based on linked control blocks
TL;DR: A DMA controller has an attached, dedicated memory as mentioned in this paper, where data objects are stored on the heap and connected by pointers, and each data object contains DMA block transfer control parameters.
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Synchronized DRAM control apparatus using two different clock rates
TL;DR: In this paper, a control apparatus for a computer is described that includes an arbiter circuit for selecting a first controller for supplying the memory of the computer with a first plurality of addresses from a first bus at first rate and for selecting the second controller for providing the memory with a second plurality of address from a second bus at a second rate.