Browse Prior Art Database

Segment Group Address

IP.com Disclosure Number: IPCOM000040194D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Beacom, TJ: AUTHOR [+3]

Abstract

Described is a Horizontal Microcode branch and a Virtual Address Translation control wherein microcode can determine the virtual address type pertaining to the concept of Segment Groups and Single Segments in a processor. A Single Segment (SID) is the virtual address range supporting 64 Kbytes starting on a 64-Kbyte boundary. A Segment Group supports a virtual address range of 256 SIDs starting on a 256-SID boundary. The complete virtual address of any byte in storage is a 48-bit address. The low-order 16-bits of this area are sufficient to address each byte within a Single Segment, and are called the Single Segment offset. The low-order 24-bits of the 48-bit virtual address are used to address each byte within a Segment Group, and are called the Segment Group offset.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 51% of the total text.

Page 1 of 2

Segment Group Address

Described is a Horizontal Microcode branch and a Virtual Address Translation control wherein microcode can determine the virtual address type pertaining to the concept of Segment Groups and Single Segments in a processor. A Single Segment (SID) is the virtual address range supporting 64 Kbytes starting on a 64-Kbyte boundary. A Segment Group supports a virtual address range of 256 SIDs starting on a 256-SID boundary. The complete virtual address of any byte in storage is a 48-bit address. The low-order 16-bits of this area are sufficient to address each byte within a Single Segment, and are called the Single Segment offset. The low-order 24-bits of the 48-bit virtual address are used to address each byte within a Segment Group, and are called the Segment Group offset. The virtual addresses supported by Segment Groups are mutually exclusive of those supported by Single Segments. The virtual addresses supporting Single Segments are any in which bits 20-23 of the 48-bit virtual addresses are '0000'B. Segment Groups are supported by all other values. The first 32 bytes of a Segment Group or a Single Segment form the Segment Group Header. Fields within this header are used by various instructions. The offset within the Segment Group or Single Segment of the Segment Group Header is '000000'X for Segment Groups and '0000'X for Single Segments, that is, a three-byte offset of zero for Segment Groups and a two-byte offset of zero for Single Segments. Other instructions execute arithmetic operations upon the 48-bit virtual addresses. If these virtual addresses are for Segment Groups, the arithmetic operations operate upon the low-order 24 bits. If these virtual addresses are for Single Segments, the arithmetic operations operate upon the low-order 16 bits. Determining and supporting differences between the 16-bit Single Segment offsets and the 24-bit Segment Group offsets are the problems solved by this invention. Segment Group Headers contain information which is accessed...