Microsoft KB Archive/67583

Requirements for Placing BUFFERS in EMS PSS ID Number: Q67583 Article last modified on 09-17-1993 PSS database name: O_MSDOS

4.00 4.01

MS-DOS

= SYMPTOMS =

If you add the /X switch to the BUFFERS= statement in your CONFIG.SYS file, the buffers are not placed in expanded memory and you receive the following error:

Error in CONFIG.SYS line x

where x identifies the line containing the erroneous entry.

= CAUSE =

This error occurs because you do not have enough free EMS memory or because your memory driver doesn’t meet the requirements of MS-DOS 4.0.

= MORE INFORMATION =

For MS-DOS version 4.0 to place the buffers into expanded memory, the following conditions must be met:


 * 1) There must be enough free EMS memory to hold all of the buffers requested. Each buffer takes approximately 524 bytes of memory, and each secondary cache buffer requires 512 bytes.
 * 2) The expanded memory driver must conform to the LIM 4.0 EMS standard. DOS requires EMS driver INT 67h functions 40h, 42h, 43h, 44h, 45h, 46h, 4fh (subfunctions 00 to 02), 53h (subfunction 1), and 58h (subfunctions 0 and 1).
 * 3) The expanded memory driver must place its Page Frame address above the 640K address line (A000:0000). The MS-DOS BUFFERS= statement requires that the page frame be in this address space for performance reasons.

If the version of DOS being used is actually IBM PC-DOS, then different requirements must be met. PC-DOS requires one fixed memory page in addition to the normal page frame to use BUFFERS /X. These memory pages are supplied by using the IBM expanded memory driver XMA2EMS.SYS in conjunction with the correct IBM XMA memory card. Please refer to the IBM PC-DOS reference manual for documentation on XMA2EMS.SYS, and requirements for the PC-DOS BUFFERS /X command.

Microsoft recommends that you avoid using BUFFERS /X under MS-DOS version 4.00 or 4.01. The SMARTDRV.SYS device driver supplied with MS-DOS versions 4.00 and 4.01 creates a disk cache that performs a comparable task, and has fewer compatibility problems.

Additional reference words: 4.00 4.01 noupd

Copyright Microsoft Corporation 1993.