Browse Prior Art Database

Channel DAT With Pin Bits

IP.com Disclosure Number: IPCOM000088685D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Ludlow, DM: AUTHOR [+2]

Abstract

By Dynamic Address Translation (DAT) virtual addresses are converted into real addresses suitable for use in a virtual storage system.

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Channel DAT With Pin Bits

By Dynamic Address Translation (DAT) virtual addresses are converted into real addresses suitable for use in a virtual storage system.

U. S. Patent 3,839,706 describes equipment for performing DAT functions relative to operations of an input/output channel. Such apparatus translates virtual addresses of commands and input/output data storage locations to real addresses. For each real storage frame, a fix-count cell is maintained which indicates current usage of the respective frame by any channel. The count is incremented when an associated page in real storage is addressed by any channel and decremented when a channel is through using that page. The zero/nonzero state of the count is used to vary a "pin" bit in the storage protect key of the associated frame so that a CPU bay not reassign (to a different virtual page) the frame in real storage while any input/output operation is in progress.

An alternative considered here would be to have the channel directly set the foregoing "pin" bit each time it initiates a reference to the associated virtual page and have alternate means associated with real storage management periodically reset the pin bits for all frames. The alternate means could then signal the channel to set the pin bits associated with all virtual pages currently in use. This "repinning" function could be performed in a piecemeal fashion by the channels (e.g., during the intervals that they would otherwise be idle). The chann...