Enabling 32-bit file access can result in slower system performance in
the following situations:
VFAT is unable to mount.
This can happen as a result of one or more of the following
problems (note that the numbers below correspond to the numbered
steps in the "VFAT is Unable to Mount" subsection of this article):
The real-mode network redirector has been loaded into memory.
A memory-resident program or device driver has a file open while
The drive is involved in a SUBST, ASSIGN, or JOIN action.
Because of the way they alter apparent disk characteristics, the
SUBST.EXE, ASSIGN.COM, and JOIN.EXE programs are not compatible with
installable file systems (IFS), such as 32-bit file access. These
utilities can't be used if 32-bit file access is enabled.
The cache size selected is too large or invalid.
Required components are missing, corrupted, or not in the specified
Windows for Workgroups version 3.11 is in a low-memory situation
after enabling VFAT.
Running VFAT/VCACHE with SMARTDrive may place Windows for
Workgroups into a low-memory situation because memory used by
SMARTDrive is not available to VCACHE.386 and vice-versa.
Since VCACHE.386 provides the caching on VFAT-enabled drives
and network drives, while SMARTDrive caches CD-ROM drives and
floppy disk drives, it is possible that systems with too large a
percentage of memory allocated to caching have some performance
If you are in a low-memory situation (that is, you are running both
SMARTDrive and VFAT), make sure that the amount of memory allocated to
SMARTDrive's WinCacheSize and the cache size allocated to VCACHE.386
do not exceed roughly 30 percent of total system RAM.
For example, on a machine with 4 megabytes (MB) RAM, if you have allocated
1024 kilobytes (K) to VCACHE, set the SMARTDrive WinCacheSize to 128K. To
do this, use a command similar to the following
c:\windows\smartdrv.exe <1024> <128>
where <1024> is the InitCacheSize (the cache size at MS-DOS) and <128>
is the size of the cache in Windows.
VFAT Is Unable to Mount
If VFAT is unable to mount, try the following:
You can unload the real-mode network redirector by typing net
stop at the MS-DOS command prompt
before starting Windows for Workgroups.
To ensure that no device driver or terminate-and-stay-resident
(TSR) program has any files open upon entering Windows for Workgroups,
clean start the machine.
For more information on clean start configurations for Windows for
Workgroups version 3.11, query on the following words in the Microsoft
wfw and clean and start
Do not use the SUBST, ASSIGN, or JOIN utilities with 32-bit file
access enabled. If you must use one of these utilities, disable 32-bit
Verify that the cache size selected is valid. For more information,
see the "Low-Memory Situation" section above.
The components used by VFAT vary depending on the system's hard disk
drive (HD) controller type and whether or not disk compression (such as
DoubleSpace, DriveSpace, or Stac Electronics Stacker) is used. If you
suspect the components are missing, corrupted, or not in the specified
directory, verify the components files sizes, or re-expand them from
your original Windows for Workgroups version 3.11 disks.
RMM.D32 11,473 (updated version of RMM.D32)
NOTE: VFAT cannot load on a volume compressed with MS-DOS 6.0
DoubleSpace. This problem was resolved in MS-DOS 6.2 and later.
IMPORTANT: The SYSTEM.INI file entries shown in the examples below are
made by Control Panel and do not require manual editing. These
examples are provided to show the component files involved and to aid
in troubleshooting. You should avoid manually editing your SYSTEM.INI
Example 1: Uncompressed WD 1003 Compatible Drive
Western Digital 1003 or ST506 compatible drives without compression
require the following entries in the [386Enh] section of the
All entries marked with an asterisk (*) are contained in the
WIN386.EXE file. All files should be located in your Windows SYSTEM
subdirectory unless otherwise noted.
Example 2: Compressed or Not WD 1003-Compatible Drive
If the drive is compressed, or if another hard disk in the machine is
not WD 1003 compatible, then the line "device=*BLOCKDEV" should be
replaced with the following:
In addition, the real mode mapper (RMM.D32) must exist in the
Windows SYSTEM subdirectory.
Example 3: Not WD 1003-Compatible Drive
If 32-bit disk access cannot be used by a particular hard disk
controller (because it is not WD 1003 compatible), the VFAT entries
for the SYSTEM.INI file's [386Enh] section should include the
VFAT is a 32-bit virtual MS-DOS file allocation table (FAT) file system and
can only mount on hard disk volumes. If 32-bit disk access drivers are not
available for a particular hard disk controller, additional handling of INT
13h calls is required. The IOS.386, VXDLDR.386, and RMM.D32 files provide
this functionality and allow VFAT/VCACHE to work on these drives. (Drives
affected include most SCSI and ESDI drives, a few IDE drives, and
compressed volumes residing on any type of hard disk.)
32-bit disk access drivers may also be provided by an original equipment
manufacturer (OEM) to work with a specific hard disk controller, replacing
Microsoft's *WDCTRL. As a troubleshooting step, these drivers should be
temporarily disabled and IOS.386, VXDLDR.386, and RMM.D32 should be used