Browse Prior Art Database

Prefix Area Renaming Assist to Avoid Address Generate Interlock

IP.com Disclosure Number: IPCOM000099532D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Emma, PG: AUTHOR [+5]

Abstract

Address Generate Interlock (AGI) occurs when the input required to generate an address is not available. This disclosure provides an alternate source for the contents of the register when the data address is in the first page of the virtual memory.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Prefix Area Renaming Assist to Avoid Address Generate Interlock

       Address Generate Interlock (AGI) occurs when the input
required to generate an address is not available.  This disclosure
provides an alternate source for the contents of the register when
the data address is in the first page of the virtual memory.

      For processor organizations that utilize register renaming (see
U.S. Patent 4,574,349) as a means of executing instructions out of
sequence while maintaining the capability to generate precise
interrupts, an opportunity exists for the registers to provide a
basis for avoiding AGI.  In particular, since the prefix area, or
first page of virtual memory, is often the source of pointers to
operating system constructs, the loading of such pointers results in
AGI when they are used by succeeding instructions in address
calculations.

      If the number of physical registers is adequate for the first-
mentioned renaming requirement, then additional physical registers
can be utilized by the processor to hold these prefix area
addressable pointers as follows:

      In the IBM System/370, any load from prefix area is
distinguished by the fact that both the base and the index (B,X)
fields of the load instruction are equal to zero.  In other
architectures, instructions that accessed commonly used system areas
will have other distinguishing characteristics.  In the case of
System/370, the displacement is hashed to the name of a set of
dedicat...