Browse Prior Art Database

Linkage Between Dissimilar Addressing Modes

IP.com Disclosure Number: IPCOM000045673D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Kern, RM: AUTHOR [+2]

Abstract

Because dynamic address translation (DAT) addresses do not usually relate to the real storage addresses, standard programming module linkage is inappropriate, and will not work.

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Linkage Between Dissimilar Addressing Modes

Because dynamic address translation (DAT) addresses do not usually relate to the real storage addresses, standard programming module linkage is inappropriate, and will not work.

Because there is no relationship between the real storage in an IBM System/370 data processing system and the virtual mapping of its users, it is necessary to create d unique program linkage to transverse a change in the DAT mode, i e., from DAT on to DAT off, or vice versa. The problem, simply stated, is that by using a store and a system mask (STNSM) instruction or a store and/or system mask (STOSM) instruction to modify the DAT control bit (i.e., PSW bit 5) requires that the next sequential instruction be addressable in both modes.

An alternative to keeping the DAT on and off code together and solving the problems of relocating addresses for specific modes can be envisioned. Essentially, separate the DAT code into two different load modules and create a new method to communicate between them. This would allow the different modules to be loaded with normal methods of relocation. It would also keep the amount of storage that must be contiguous (because of DAT-off requirements) to a minimum, and in fact not even require that it be mapped in virtual. What must be created is a method for bridging these modules at execution time.

To perform this linkage, several problems with the current linkage must be solved. First, an area of storage must be identified which has the same address in real and virtual. Since it is very unlikely that...