Specifications

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OpenVMS Operating System for Alpha and VAX (Versions 7.1, 7.1–1H1, 7.1–1H2, and 7.1–2) SPD 41.87.06

64-Bit Virtual Addressing (Alpha Only)

The OpenVMS Alpha operating system provides sup-

port for 64-bit virtual memory addressing. This capa-

bility makes the 8TB virtual address space, deﬁned by

the Alpha architecture, available to the OpenVMS Alpha

operating system and to application programs. Future

hardware implementations will provide greater capacity.

OpenVMS Alpha compilers and applications take ad-

vantage of 64-bit processing by using 64-bit data types.

Refer to the SPDs for the OpenVMS Alpha compilers

for further details. Note the application-virtual address

space defaults to a 32-bit implementation for compata-

bility and migration purposes.

Very Large Memory (VLM) Features (Alpha Only)

OpenVMS Alpha Version 7.1 builds on the Version 7.0

VLM support and provides the following extended, ad-

ditional memory management VLM features:

• Memory-resident global sections

• Shared page tables

• Expandable global page table

• Reserved memory registry

Memory-resident global sections allow a database

server to keep larger amounts of "hot" data cached in

physical memory. The database server then accesses

the data directly from physical memory without perform-

ing I/O read operations from the database ﬁles on disk.

With faster access to the data in physical memory, run-

time performance increases dramatically.

Shared page tables allow that same database server

to reduce the amount of physical memory consumed

within the system. Because multiple server processes

share the same physical page tables that map the large

database cache, an OpenVMS Alpha system can sup-

port more server processes. This increases overall sys-

tem capacity and decreases response time to client re-

quests.

Also, with shared page tables, the database server

startup time is dramatically reduced because server pro-

cesses can map memory-resident global sections hun-

dreds of times faster than traditional global sections.

With a multiple giga-byte global database cache, the

server startup performance gains can be signiﬁcant.

As of OpenVMS Alpha Version 7.1, the system param-

eters GBLPAGES and GBLPAGFIL have been modi-

ﬁed to become dynamic parameters. Users with the

CMKRNL privilege can now change these parameter

values on a running system. Increasing the value of the

GBLPAGES parameter will allow the global page table

to expand, on demand, up to the new maximum size.

The Reserved Memory Registry supports memory-

resident global sections and shared page tables.

Through its interface within the SYSMAN utility, the Re-

served Memory Registry allows an OpenVMS system to

be conﬁgured with large amounts of memory set aside

for use within memory-resident sections or other privi-

leged code. The Reserved Memory Registry also allows

an OpenVMS system to be properly tuned through AU-

TOGEN, thus accounting for the pre-allocated reserved

memory.

Extended Physical Addressing (VAX Only)

With OpenVMS VAX Version 6.0, physical address

space was extended from 30 bits to 32 bits. The

OpenVMS VAX operating system can provide 3.5 GB of

physical memory and .5 GB of I/O and adapter space.

This enables large applications and workloads to access

the large amounts of physical memory that they require.

The following table lists the VAX processors that support

this extended physical addressing.

System

Accessible

Physical

Memory

I/O and Adapter

Space

VAX 6000 model 600 1.25 GB .5 GB

VAX 7000 series 3.5 GB .5 GB

VAX 10000 series 3.5 GB .5 GB

Vector Processing (VAX Only)

A single data item with only one value is known as a

scalar value. A group of related scalar values, or ele-

ments, with the same data type, is known as a vector.

An extension to the VAX architecture deﬁnes an op-

tional design for integrated vector processing that has

been adopted by several VAX systems. The VAX vec-

tor architecture includes sixteen 64-bit vector registers

(V0 through V15), each containing 64 elements; vector

control registers; vector function units; and a set of vec-

tor instructions. VAX vector instructions transfer data

between the vector registers and memory; perform inte-

ger and ﬂoating-point arithmetic; and execute processor

control functions.

A more detailed description of the VAX vector architec-

ture, vector registers, and vector instructions appears in

the VAX MACRO and Instruction Set Reference Manual.

The OpenVMS VAX operating system provides fully

shared, multiprogramming support for VAX vector pro-

cessing systems. By default, OpenVMS VAX loads vec-

tor support code when initializing vector-present sys-

tems but does not load it when initializing vector-absent

systems. System managers can control this behavior

by using the VECTOR_PROC system parameter.