Using read current transactions for improved performance in directory-based coherent I/O systems
US6647469B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | May 1, 2000 |
| Grant date | Nov 11, 2003 |
| Priority date | — |
| Expiry date | May 1, 2020 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F2212/621
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A shared memory provides data access to a plurality of agents (e.g., processor, cells of processors, I/O controllers, etc.) and includes a memory and a memory controller. The memory controller selectively provides memory access to the agents in both coherent and read current modes of operation. In the coherent mode, the memory controller ensures that the data stored in system memory is accurately and precisely mirrored in all subservient copies of that data as might typically be stored in agent cache memories. Using, for example, a MESI type protocol, the memory controller limits access to memory so that only an “owner” or a particular portion or line of memory has write access and that, during the extension of these write privileges, no other agent has a valid copy of the data subject to being updated. Thus, the memory controller implements a first set of rule in the coherent mode of operation to insure that all copies of data stored by the agents are coherent with data stored in the memory. In a read current mode of access, a read-once segment of data is copied to an agent with the agent implementing a second set of rules to minimize or eliminate the possibility that …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.