Storage fetch protect override controls
US4472790A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 5, 1982 |
| Grant date | Sep 18, 1984 |
| Priority date | — |
| Expiry date | Feb 5, 2002 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F12/1475
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
The embodiment provides selective supervisory disablement of fetch protection for a special storage subarea (such as for the first half of the first 4KB block) while fetch protection is enabled for an area containing the subarea by a single storage protect key. That is, the fetch protect for the subarea (normally provided in the fetch protect for the entire area) by the area's protect key is overriden by the selective subarea disablement control, so that accesses to the subarea are not fetch protected by the storage key. The override protection control is secured by its enablement via a field position in a control register only accessible to supervisory programming. Thus, while fetch protection is set on for a predefined 4KB block, the fetch protect override controls can disable the fetch protection for a portion of the block's real addresses (e.g. addresses 0-2047).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.