Microsoft KB Archive/21690

Word’s Use of Conventional, Extended, and Expanded Memory

PSS ID Number: Q21690 Article last modified on 11-02-1994

3.x 4.00 5.00 5.50 6.00

MS-DOS

= SUMMARY =

The following are three types of memory being used on PCs:

  Conventional memory is the standard memory up to 640K that DOS and most applications are able to recognize.   Extended memory is used when more than 640K has been added to a computer via slots/sockets on the motherboard of the computer or through the use of an extended memory card. Extended memory is primarily for use by operating systems such as OS/2 and is not normally available to regular DOS programs. Extended memory can be added to a 286 processor computer (up to 16 MB), or to a 386 or 486 processor computer (up to 4 GB). Extended memory is not possible on an 8088/8086 processor computer. Most computers and memory cards come with device drivers that can utilize extended memory as a RAM drive or a print spooler in the DOS environment. Other drivers are available that can convert extended memory into expanded memory, or provide a disk cache function.   Expanded memory is also added to a computer via slots/sockets on the motherboard of the computer (rarely), or through the use of an expanded memory card. Expanded memory is implemented as a pool of memory outside the normal address space of the computer, and bank switched into a conventional memory “window” for use by programs. Once the expanded memory is installed, a device driver is loaded to manage this expanded memory pool. Any program that uses expanded memory must be specifically written to do so following the Lotus-Intel-Microsoft (LIM) specifications. In addition to application programs, many device drivers, such as RAM drives, print spoolers, and disk caches, can also use expanded memory for their memory needs. Support of expanded memory began with version 5.00. In OS/2, support for extended memory began with Word version 5.00. 

KBCategory: kbother KBSubcategory: Additional reference words:

=
================================================================ Copyright Microsoft Corporation 1994.