Storage fetch protect override controls

Details Storage fetch protect override controls Storage fetch protect override controls

1982-02-05

1984-09-18

Zache, Raulfe B.

Boots, shoes, and leggings

G06F 900, G06F 1300

Patent

active

044727909

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).

REFERENCES:
patent: 3905023 (1975-09-01), Perpiglia
patent: 4038645 (1977-07-01), Birney et al.
patent: 4104721 (1978-08-01), Markstein et al.
patent: 4135240 (1979-01-01), Ritchie
patent: 4293910 (1981-10-01), Flusche et al.
patent: 4355355 (1982-10-01), Butwell et al.
patent: 4366537 (1982-12-01), Heller et al.
patent: 4430705 (1984-02-01), Cannavino et al.

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