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1. 32 BIT VERSIONS OF WINDOWS SOFTWARE
2. 32 BIT VERSIONS OF WINDOWS CODE
3. 32 BIT VERSIONS OF WINDOWS WINDOWS

It helps to keep 32-bit programs from accidentally accessing the data of 64-bit ones. The WoW64 subsystem isolates 32-bit programs from 64-bit ones by redirecting calls to files and the register. Well, the same 32-bit program built on a 64-bit system can allocate almost 4 Gbytes of memory (in practice it is usually about 3.5 Gbytes).

32 BIT VERSIONS OF WINDOWS WINDOWS

Maybe you know that a program built with the switch "/LARGEADDRESSAWARE:YES" can allocate up to 3 Gbytes of memory, if a 32-bit Windows is launched with the switch "/3gb". However, simple 32-bit applications can still get one benefit of being executed in the 64-bit environment.

Benefits of the 64-bit environment for 32-bit programsīecause of the WoW64 layer, 32-bit programs are less efficient in the 64-bit environment than in their native 32-bit one. For an average program, you may expect a 5-15% performance gain after recompilation alone. This is explained by architectural modifications in the microprocessor, such as an increased number of general-purpose registers.

32 BIT VERSIONS OF WINDOWS CODE

Two per cent is not very much, but keep in mind that 32-bit applications work a bit slower under the 64-bit Windows than in the 32-bit environment.Ĭompilation of 64-bit code does not only allow you to avoid using WoW64, but also gives you an additional performance gain. For an average program, you may expect 2% performance penalty because of this layer. In some places this layer is thin, in others a bit thicker. In this case the WoW64 subsystem emulates only the 32-bit environment through an additional layer between a 32-bit application, and the 64-bit Windows API. WoW64 on Intel 64 (AMD64 / 圆4) does not require instruction emulation. This emulation is rather resource-intensive in comparison to WoW64 for Intel 64 architecture, because the system has to switch from the 64-bit mode to compatibility mode when executing 32-bit programs. For example, the 64-bit Windows version developed for Intel Itanium 2 processor, employs WoW64 to emulate x86 instructions. kernel-mode programs compiled for 32-bit operating systems.ĭifferent processor architectures have a bit different WoW64.programs compiled for 16-bit operating systems.

The WoW64 subsystem does not support the following programs: WoW64 (Windows-on-Windows 64-bit) is a subsystem of Windows operating system, which allows you to execute 32-bit applications on all the 64-bit versions of Windows. Backward compatibility is arranged through the mechanisms implemented in WoW64.

32 BIT VERSIONS OF WINDOWS SOFTWARE