IBM Mainframe Expanded Storage
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High Quality Content by WIKIPEDIA articles! Traditionally IBM Mainframe memory has been byte-accessible. This kind of memory is termed "Central Storage". IBM Mainframe processors - through much of the 1980s and 1990s - supported another kind of memory - Expanded Storage. Expanded Storage is 4KB-page addressable. When an application wants to access data in Expanded Storage it must first be moved into Central Storage. Similarly, data movement from Central Storage to Expanded Storage is done in multiples of 4KB pages. Initially page movement was performed using relatively expensive instructions. ...
High Quality Content by WIKIPEDIA articles! Traditionally IBM Mainframe memory has been byte-accessible. This kind of memory is termed "Central Storage". IBM Mainframe processors - through much of the 1980s and 1990s - supported another kind of memory - Expanded Storage. Expanded Storage is 4KB-page addressable. When an application wants to access data in Expanded Storage it must first be moved into Central Storage. Similarly, data movement from Central Storage to Expanded Storage is done in multiples of 4KB pages. Initially page movement was performed using relatively expensive instructions. In 1989, however, the MVPG (Move Page) instruction was introduced, decreasing the cost for single page moves. In 1992 the ADMF (Asynchronous Data Mover Facility) was introduced - to reduce the cost of moving groups of pages between Central and Expanded Storage.
