Forward progress on retried snoop hits by altering the coherency state of a local cache
US6138218A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 17, 1998 |
| Grant date | Oct 24, 2000 |
| Priority date | — |
| Expiry date | Feb 17, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F12/0811
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
When a device snooping the system bus of a multiprocessor system detects an operation requesting data which is resident within a local memory in a coherency state requiring the data to be sourced from the device, the device attempts a intervention. If the intervention is impeded by a second device asserting a retry, the device sets a flag to provide historical information regarding the failed intervention. On a subsequent snoop hit to the same cache location, if the device again asserts an intervention and the snooped operation is again retried, the device undertakes an action to alter the coherency state of the requested cache item towards an ultimate coherency state expected to be the result of the original operation requesting the cache item. In the case where the requested cache item includes modified data resident in the device's local memory, the action may include a push operation writing the requested cache item to system memory. This operation may be snooped by other devices from the system bus to update their local memories. In the case where the requested cache item includes data in a coherency state other than the modified state, the action may include simply altering t…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.