Browse Prior Art Database

Address Space Map Array for Computer Systems With Extended Memory Addressing

IP.com Disclosure Number: IPCOM000061639D
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Kurtz, HL: AUTHOR [+3]

Abstract

A technique is described whereby a program visible facility, called an address space map array, is used in computer systems which require extended addressing capability to map the location and size of active segment tables which are in real storage. There are 256 entries in the array, one per address space. During address translation, an active Space Identifier (SID) is used to select the entry. Each entry has 36 bits and has the following format. (Image Omitted) Bit 0 This bit when set to 1 indicates a valid active address space. An attempt to access this space when the bit is off will cause a program check. Bits 1-22 This 22-bit field contains a real address. It is the origin address of the associated Segment Table which can start on any four-byte boundary in a 16-megabyte real address space.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Address Space Map Array for Computer Systems With Extended Memory Addressing

A technique is described whereby a program visible facility, called an address space map array, is used in computer systems which require extended addressing capability to map the location and size of active segment tables which are in real storage. There are 256 entries in the array, one per address space. During address translation, an active Space Identifier (SID) is used to select the entry. Each entry has 36 bits and has the following format.

(Image Omitted)

Bit 0 This bit when set to 1 indicates a valid active address space. An attempt to access this space when the bit is off will cause a program check. Bits 1-22 This 22-bit field contains a real address. It is the origin address of the associated Segment Table which can start on any four-byte boundary in a 16-megabyte real address space. Bits 23-35 This 13-bit field contains a number which specifies the length of the Segment Table in entries which are four bytes each. Programming insures that the contents of an entry properly reflect the state of the associated Segment Table before any accesses are made to the address space mapped by it.

1

Page 2 of 2

2

[This page contains 1 picture or other non-text object]