04959774 is referenced by 170 patents and cites 16 patents.

A highly reliable shadow memory system is able to survive multiple fast sequence power failures and includes a volatile main memory and a shadow memory subsystem which continually monitors write accesses to the main memory. The shadow memory subsystem includes a disk drive or shadow memory storing a copy of the data in main memory. As the main memory contents are altered, the shadow memory is continually updated to reflect the changes while main utility power is available. In the event of a main utility power failure, backup power is required to store main memory data in the shadow memory for only a few storage locations for which the updating of the shadow memory may lag main memory data changes. Consequently, only a small portion of available battery backup power is required to preserve all main memory data and the system can withstand multiple rapid succession power failures without loss of data.

Title
Shadow memory system for storing variable backup blocks in consecutive time periods
Application Number
628417
Publication Number
4959774
Application Date
June 30, 1989
Publication Date
September 25, 1990
Inventor
John E Davis
Reseda
CA, US
Assignee
Ampex Corporation
CA, US
IPC
G06F 12/16
G06F 11/30
G06F 15/00
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