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Q81377: SMARTDrive /double_buffer Cannot Load into UMBs

Article: Q81377
Product(s): Microsoft Windows 95.x Retail Product
Version(s): WINDOWS:3.1,3.11
Operating System(s): 
Keyword(s): 
Last Modified: 15-OCT-1999

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The information in this article applies to:

- Microsoft Windows versions 3.1, 3.11 
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SYMPTOMS
========

Attempting to load SMARTDrive version 4.0 (SMARTDRV.EXE) as a double-buffer
driver into the upper memory area (UMA) generates the following error message:

  Double buffering driver cannot be loaded into a UMB. Do not use the
  devicehigh command or other load-high utilities to load Smartdrv.exe.

CAUSE
=====

When loaded in the CONFIG.SYS file as a device driver to provide double
buffering, SMARTDRV.EXE must be loaded in conventional or low memory. Even if a
memory manager is present that allows programs to be loaded into the UMA,
SMARTDRV.EXE must be loaded low if it is being used as a double-buffering device
driver.

NOTE: There is no workaround for this problem.

MORE INFORMATION
================

The double buffering that SMARTDRV.EXE provides is required for certain Bus
Master disk controllers when running in the Virtual 8086 mode of the 80386 and
80486 processors.

Improved compatibility between Virtual 8086 mode and these older controllers
depends on the fact that the buffer (approximately 2K) that SMARTDrive uses for
the purposes of double buffering loads into an address that is identical to its
location in physical memory.

386 memory managers, such as EMM386.EXE, allow you to load device drivers and
terminate-and-stay-resident (TSR) programs into upper memory blocks (UMBs) by
using the ability of 80386 and 80486 processors to remap addresses between 640K
and 1024K into physical extended memory. Because this reassigning of addresses
would prevent SMARTDRV.EXE's double buffer from residing at an address
compatible with its location in physical memory, SMARTDRV.EXE must remain in
conventional memory.

NOTE: This information does not apply if you are using SMARTDRV.EXE version 4.0
as a disk cache in the AUTOEXEC.BAT file. The ability to provide double
buffering is independent of SMARTDRV.EXE's role as a disk cache. You can load
SMARTDRV.EXE with the /double_buffer option low in the CONFIG.SYS file, and load
SMARTDRV.EXE, the disk cache, high in the AUTOEXEC.BAT file.

For more information on double buffering and SMARTDRV.EXE, query on the following
words in the Microsoft Knowledge Base:

  smartdrv.exe and double and buffer and bus and mastering

KBCategory: kbother kbinterop
KBSubcategory: win31

Additional query words: 3.10 SCSI winmem 3.11

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Keywords          :  
Technology        : kbWin3xSearch kbZNotKeyword3 kbWin310 kbWin311
Version           : WINDOWS:3.1,3.11

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