Apparatus and method of maintaining cache coherency in a multi-processor computer system with global and local recently read states
US6018791A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 17, 1998 |
| Grant date | Jan 25, 2000 |
| Priority date | — |
| Expiry date | Feb 17, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F12/0831
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A multi-processor computer system with clustered processing units uses a cache coherency protocol having a "recent" coherency state to indicate that a particular cache block containing a valid copy of a value (instruction or data) was the most recently accessed block out of a group of cache blocks in different caches (but at the same cache level) that share valid copies of the value. The "recent" state can advantageously be used to implement optimized memory operations such as intervention, by sourcing the value from the cache block in the "recent" state, as opposed to sourcing the value from system memory (RAM), which would be a slower operation. In an exemplary implementation, the hierarchy has two cache levels supporting a given processing unit cluster; the "recent" state can be applied to a plurality of caches at the first level (each associated with a different processing unit cluster), and the "recent" state can further be applied to one of the caches at the second level.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.