RU/2: Форум. Общение пользователей и разработчиков OS/2 (eCS). : 32/64 bit


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From : Sanych
To : All
Subj : 32/64 bit
Есть дока на интеле (ссылку не помню) 253665.pdf
"Intel® 64 and IA-32 Architectures Software Developer’s Manual"
Там много чего написано про 64 бита.
в частности:
"3.1.1 Intel® 64 Architecture
Intel 64 architecture adds IA-32e mode. IA-32e mode has two sub-modes. These
are:
• Compatibility mode (sub-mode of IA-32e mode) — Compatibility mode
permits most legacy 16-bit and 32-bit applications to run without re-compilation
under a 64-bit operating system. For brevity, the compatibility sub-mode is
referred to as compatibility mode in IA-32 architecture. The execution
environment of compatibility mode is the same as described in Section 3.2.
Compatibility mode also supports all of the privilege levels that are supported in
64-bit and protected modes. Legacy applications that run in Virtual 8086 mode or
use hardware task management will not work in this mode.
Compatibility mode is enabled by the operating system (OS) on a code segment
basis. This means that a single 64-bit OS can support 64-bit applications running
in 64-bit mode and support legacy 32-bit applications (not recompiled for
64-bits) running in compatibility mode.
Compatibility mode is similar to 32-bit protected mode. Applications access only
the first 4 GByte of linear-address space. Compatibility mode uses 16-bit and 32-
bit address and operand sizes. Like protected mode, this mode allows applications
to access physical memory greater than 4 GByte using PAE (Physical
Address Extensions).
• 64-bit mode (sub-mode of IA-32e mode) — This mode enables a 64-bit
operating system to run applications written to access 64-bit linear address
space. For brevity, the 64-bit sub-mode is referred to as 64-bit mode in IA-32
architecture.
64-bit mode extends the number of general purpose registers and SIMD
extension registers from 8 to 16. General purpose registers are widened to 64
bits. The mode also introduces a new opcode prefix (REX) to access the register
extensions. See Section 3.2.1 for a detailed description.
64-bit mode is enabled by the operating system on a code-segment basis. Its
default address size is 64 bits and its default operand size is 32 bits. The default
operand size can be overridden on an instruction-by-instruction basis using a REX
opcode prefix in conjunction with an operand size override prefix.
REX prefixes allow a 64-bit operand to be specified when operating in 64-bit
mode. By using this mechanism, many existing instructions have been promoted
to allow the use of 64-bit registers and 64-bit addresses."

Fri 24 Aug 2007 11:19 Mozilla/5.0 (Windows; U; Windows NT 5.1; ru; rv:1.8.1.6) Gec



Programmed by Dmitri Maximovich, Dmitry I. Platonoff, Eugen Kuleshov.
25.09.99 (c) 1999, RU/2. All rights reserved.
Rewritten by Dmitry Ban. All rights ignored.