Translator having segment bounds encoding for storage in a TLB
US5652872A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 8, 1995 |
| Grant date | Jul 29, 1997 |
| Priority date | — |
| Expiry date | May 8, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F12/1036
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A computer system emulates segment bounds checking with a paging system. Pages entirely within a segment are designated as `clear pages`, while the first and last pages containing segment bounds may be partially-valid pages. The computer system has a memory with a segment descriptor table and an active segment descriptor cache. The active segment descriptor cache holds a copy of the segment descriptors for the active segments in a central processing unit (CPU). The active segment descriptor cache also hold the first and last clear page numbers and the first and last linear address offsets for the active segment. A software segment load routine copies portions of the segment descriptor from the segment descriptor table to the active segment descriptor cache when a user program loads a new segment. Only the segment base address is copied to the CPU die; the segment limit and selector need not be stored on the CPU die. The CPU has a translation-lookaside buffer (TLB) that includes bounds fields and a comparator for signaling when an offset portion of a linear address is outside the bound on a page. A TLB miss routine compares the linear address to the first and last clear pages in the…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.