Address Windowing Extensions
Encyclopedia
Address Windowing Extensions (AWE) is a Microsoft Windows
application programming interface
that allows a 32-bit software application
to access more physical memory than it has virtual address space. The process of mapping an application's virtual address space to physical memory under AWE is known as "windowing," and is similar to the "overlay" concept of other environments. AWE is beneficial to certain data
-intensive applications, such as database
management systems and scientific and engineering
software, that need to manipulate very large data set
s.
The application reserves a region, or "window" of virtual address space, and allocates one or more regions of physical memory. Using the AWE API, the application can map the virtual window to any one of the physical regions. The application can reserve more than one virtual address space and map it to any of the allocated regions of physical memory, as long as the number of bytes reserved in the virtual address space matches that of the physical memory region.
AWE usage is coded into the application itself. An application must have the Lock Pages in Memory privilege to use AWE.
AWE does depends on Physical Address Extension
support when reserving memory above 4 GB.
An article published in Dr. Dobb's Journal
in 2004 noted that memory allocated using Address Windowing Extensions will not be written to the pagefile, and suggested that AWE regions could therefore be used as a way of protecting sensitive application data such as encryption keys.
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
application programming interface
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
that allows a 32-bit software application
Application software
Application software, also known as an application or an "app", is computer software designed to help the user to perform specific tasks. Examples include enterprise software, accounting software, office suites, graphics software and media players. Many application programs deal principally with...
to access more physical memory than it has virtual address space. The process of mapping an application's virtual address space to physical memory under AWE is known as "windowing," and is similar to the "overlay" concept of other environments. AWE is beneficial to certain data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
-intensive applications, such as database
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
management systems and scientific and engineering
Engineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...
software, that need to manipulate very large data set
Data set
A data set is a collection of data, usually presented in tabular form. Each column represents a particular variable. Each row corresponds to a given member of the data set in question. Its values for each of the variables, such as height and weight of an object or values of random numbers. Each...
s.
The application reserves a region, or "window" of virtual address space, and allocates one or more regions of physical memory. Using the AWE API, the application can map the virtual window to any one of the physical regions. The application can reserve more than one virtual address space and map it to any of the allocated regions of physical memory, as long as the number of bytes reserved in the virtual address space matches that of the physical memory region.
AWE usage is coded into the application itself. An application must have the Lock Pages in Memory privilege to use AWE.
AWE does depends on Physical Address Extension
Physical Address Extension
In computing, Physical Address Extension is a feature to allow x86 processors to access a physical address space larger than 4 gigabytes....
support when reserving memory above 4 GB.
An article published in Dr. Dobb's Journal
Dr. Dobb's Journal
Dr. Dobb's Journal was a monthly journal published in the United States by CMP Technology. It covered topics aimed at computer programmers. DDJ was the first regular periodical focused on microcomputer software, rather than hardware. It later became a monthly section within the periodical...
in 2004 noted that memory allocated using Address Windowing Extensions will not be written to the pagefile, and suggested that AWE regions could therefore be used as a way of protecting sensitive application data such as encryption keys.
External links
- Address Windowing Extensions on MSDN
- Address Windowing Extensions CodingCodingCoding may refer to:* Channel coding in coding theory* Line coding* Computer programming, the process of designing, writing, testing, debugging / troubleshooting, and maintaining the source code of computer programs...
Example