Microsoft KB Archive/49740

EMM386.SYS Does Not Support Page Frames 254 and 255 PSS ID Number: Q49740 Article last modified on 01-20-1993 PSS database name: O_MSDOS

4.00 4.01

MS-DOS

Summary:

It is not possible to specify pages 254 and 255 with the EMM386.SYS driver. This mode of operation is not supported by EMM386.SYS. However, this mode is supported by the XMA2EMS.SYS driver.

The XMA2EMS.SYS driver supports this mode by naming the pages so that applications and system programs can share pages by referencing a name instead of passing handles. Pages 254 and 255 are actually two EMS pages that are logically named P254 and P255. The logical names are used by all of the programs involved so they can identify the same pages. For more information on how this is done, please see the LIM 4.0 EMS specification.

These two pages, P254 and P255, are reserved for IBM PC-DOS system use. P254 is used by FASTOPEN when used in conjunction with EMS, and P255 is used by BUFFERS when used in conjunction with EMS. This feature is unique to IBM PC-DOS 4.0x. MS-DOS 4.00 and 4.01 do not operate in this fashion.

Further information on these drivers is located in the README.TXT file included with the Microsoft MS-DOS Packaged Product Versions 4.00 and 4.01. XMA2EMS.SYS is documented in the 4.01 README.TXT file, but not the 4.00 README.TXT file.

Additional reference words: 4.00 4.01 noupd

Copyright Microsoft Corporation 1993.