Patent ES-8307055-A1 (ES)
Title: Key storage error processor for main page memory
IPC: G06F11/00
Filed: 1982-09-17
Abstract: EP--76098 A The reference bit (R) of the main storage key (K) indicates whether the corresponding page (P) has been accessed, whilst the change bit (C) indicates whether information has been written into the page. Respective parity bits are added to the reference bit and to the change bit to form the main storage key, and a parity check occurs when the main storage key is read out. - If a parity error is detected, then the reference bit is set to indicate an access and the change bit is set to indicate a store, which shows that the page has been updated. A new parity bit is added to the set reference bit, and the main storage key is then rewritten. As a result, when an error is detected by parity check of the bit pair of the reference bit, or the change bit, and the parity bit, then a logic one is sent to an access control unit. The reference bit alternatively of the or the change bit, is then set to a logic one and the parity bit is set to a zero. This achieves a state in which the corresponding page is given a reduced priority for save. Then the main storage key is rewritten.  (1/5) EPAB- EP--76098 B The reference bit (R) of the main storage key (K) indicates whether the corresponding page (P) has been accessed, whilst the change bit (C) indicates whether information has been written into the page. Respective parity bits are added to the reference bit and to the change bit to form the main storage key, and a parity check occurs when the main storage key is read out. - If a parity error is detected, then the reference bit is set to indicate an access and the change bit is set to indicate a store, which shows that the page has been updated. A new parity bit is added to the set reference bit, and the main storage key is then rewritten. As a result, when an error is detected by parity check of the bit pair of the reference bit, or the change bit, and the parity bit, then a logic one is sent to an access control unit. The reference bit alternatively of the or the change bit, is then set to a logic one and the parity bit is set to a zero. This achieves a state in which the corresponding page is given a reduced priority for save. Then the main storage key is rewritten. (20pp Dwg.No.1/5) - EP--76098 B A key storage error processing system for a system which is provided with a key storage having stored therein main storage keys respectively corresponding to pages into which a main storage is divided, each main storage key having at least a reference bit indicating whether the corresponding page has been accessed and a change bit indicating whether information has been written into the page; in which system:-respective parity bits are added to the reference bit and the change bit to form the main storage key; and which system comprises:- detecting means for detecting a parity error in a pair consisting of the reference bit concerned and its associated parity bit and a pair consisting of the change bit concerned and its associated parity bit, when a main storage key is read out; and characterised in that it comprises means for rewriting the main storage key after setting the reference bit concerned to a value indicating that the corresponding page has been accessed and adding a new parity bit to the thus set reference bit, when a parity erorror is detected by the detecting means in the pair consisting of the reference bit concerned and its associated parity bit, and/or after setting the change bit concerned to a value indicating that the corresponding page has been written into and adding a new parity bit to the thus set change bit, when a parity error is detected in the pair consisting of the change bit concerned and its associated parity bit.  (10pp) USAB- US4514847 A The system comprises a detector connected to a key storage, for detecting a parity error in a pair of the reference bit and the parity bit and a pair of the change bit andthe parity bit when the main storage key is read out and a device is connected to the key storage and the detecting rewrites themain storage key after setting the reference bit to a state indicating access to the corresponding page and adding a new parity bit to the reference bit when a parity error is detected in the pair of the regerence bit and the parity bit. - The change bit is set to a state indicating the write in the corresponding page and a new parity bit  is added to the change bit when a parity error is detected in the pair of the change bit and theparity bit.