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SmartDrv is disk caching utility that made use of EMS or XMS on 80286 and higher PCs. It has shipped with all versions of Windows since Windows/286 (2.11) and MS-DOS since 4.01.

The impact on disk performance could be dramatic, since disks at that time, especially MFM and RLL disks, typically had no cache, and because the FAT file system (without SMARTDRV) cached disk accesses though Buffers - the FAT itself being a potential victim.

Version History

Version Specification
2.1 Ships with Microsoft MS-DOS version 4.01.
  • Provides read cache for BIOS-supported hard disks only.
  • Can use extended or expanded memory for cache.
3.0 Ships with Microsoft Windows versions 3.0 and 3.0a.
  • Same as SMARTDrive 2.1, plus:
  • Provides support for double-buffering.
3.13 Ships with Microsoft MS-DOS versions 5.0 and 5.0a.
  • Same as SMARTDrive 3.0, plus:
  • Provides added detection for logical partitioning.
  • Includes code tuning.
4.0 Ships with Microsoft Windows versions 3.1 and 3.11.
  • Same as SMARTDrive 3.13, plus:
  • Cache loads in AUTOEXEC.BAT as SMARTDRV.EXE and automatically attempts to load high.
  • Double-buffering support loads in CONFIG.SYS as:
    • Device=<drive>\<path>\SMARTDRV.EXE /Double_Buffer
  • Read and write cache for all drives supported by the device driver interface, including floppy drives.
4.1 Ships with Microsoft MS-DOS version 6.0.
  • Same as SMARTDrive 4.0, plus:
  • Includes support for DoubleSpace drives.
4.2 Available through online services only.
  • Same as SMARTDrive 4.1, plus:
  • Includes support to clear the cache at an MS-DOS prompt.
  • Global write cache disabled by default.
5.0 Ships with Microsoft MS-DOS versions 6.20 and 6.21, and with Microsoft Windows for Workgroups version 3.11.
  • Same as SMARTDrive 4.2, plus:
  • Supports read-caching CD-ROM drives.
  • Supports the /u switch to not cache CD-ROM drives.
5.01 Ships with Microsoft MS-DOS version 6.22.
  • Same as SMARTDrive 5.0, plus:
  • Fixes problems with Kodak Photo CDs.
  • Includes support for DoubleSpace and DriveSpace drives.

Table Source:


SMARTDRV.SYS shipped was loaded in config.sys.


With Windows 3.1, SMARTDRV.EXE replaced SMARTDRV.SYS and is loaded in autoexec.bat unless double-buffering (which is used to provide caching to disks that do not support 32-bit IO on 80386 or higher processors) is required.


[drive:][path]SMARTDRV [/X] [[drive[+|-]]...] [/U] [/C|/R] [/F|/N] [/L]
[/V|/Q|/S] [InitCacheSize[WinCacheSize]] [/E:ElementSize]

Once SMARTDrive is running, use the following syntax:

SMARTDRV [/X] [[drive[+|-]]...] [/C|/R] [/F|/N] [/Q|/S]

To view the current status after SMARTDrive has loaded, use the following syntax:



Parameter Function
[drive:][path] Specifies the location of the SMARTDRV.EXE file.
[[drive]+|-] Specifies the letter of the disk drive for which you want to control caching. Include the plus (+) sign to enable caching for the specified drive; include the minus (-) sign to disable caching for that drive. You can specify multiple disk drives. If you specify a drive letter without a plus or minus sign, read-caching is enabled and write-caching is disabled. If you specify a drive letter followed by a plus sign (+), read-caching and write-caching are enabled. If you specify a drive letter followed by a minus sign (-), both read-caching and write-caching are disabled. If you don't specify a drive letter, floppy disk drives, CD-ROM drives, and drives created using Interlnk are read-cached but not write-cached, hard disk drives are both read-cached and write-cached, and network drives and Microsoft Flash memory-card drives are ignored. (For information about how DriveSpace caches compressed drives, see Notes.)
InitCacheSize Specifies the size in kilobytes of the cache when SMARTDrive starts (when Windows is not running). The size of the disk cache affects how efficiently SMARTDrive runs. In general, the larger the cache, the less often SMARTDrive needs to read information from the disk, which speeds up your system's performance. If you do not specify an InitCacheSize value, SMARTDrive sets the value according to how much memory your system has (see the table below).
WinCacheSize Specifies, in kilobytes, how much SMARTDrive will reduce the cache size for Windows. When you start Windows, SMARTDrive reduces the size of the cache to recover memory for Windows' use. When you quit Windows, the cache returns to its normal size. WinCacheSize specifies the smallest size to which SMARTDrive will reduce the cache. The default value depends on how much available memory your system has (see the table below). If you specify a value for InitCacheSize that is smaller than the value specified for WinCacheSize, InitCacheSize<.tt> is set to the same size as <tt>WinCacheSize.

The following table shows what the default values for InitCacheSize and WinCacheSize will be, depending on the amount of available extended memory your computer has.

Extended Memory InitCacheSize WinCacheSize
Up to 1 MB All extended Zero (no caching)
Up to 2 MB 1 MB 256K
Up to 4 MB 1 MB 512K
Up to 6 MB 2 MB 1 MB
>= 6 MB 2 MB 2 MB


Switch Purpose
/X Disables write-behind caching for all drives. You can then enable caching for individual drives by using the [[drive]+|-] parameter.
/U Does not load the CD-ROM caching module of SMARTDrive even if you have a CD-ROM drive. If SMARTDrive is loaded with the /U switch, you cannot enable CD-ROM drive caching. If SMARTDrive is loaded without the /U switch, you can disable or enable caching individual CD-ROM drives using the [[drive]+|-] parameter.
/C Writes all cached information from memory to cached disks. SMARTDrive writes information from memory to the disk at times when other disk activity has slowed. You might use this option if you are going to turn off your computer and want to make sure all cached information has been written to the disk. (SMARTDrive writes all cached information to the disk if you restart your computer by pressing CTRL+ALT+DELETE, but not if you simply turn off the power or press your computer's reset button.)
/R Clears the contents of the existing cache, including writing all write-cached information to disk, and restarts SMARTDrive.
/F Writes cached data after each command completes. This is the default value.
/N Writes cached data when the system is idle. When the command prompt returns, not all cached data may be written yet. To ensure that all the cached data is written, use the /C switch.
/L Prevents SMARTDrive from automatically loading into upper memory blocks (UMBs), even if there are UMBs available. You can use the /L switch if upper memory is enabled for use by programs. If you are using SMARTDrive's double-buffering feature and your system appears to be running slowly, try adding the /L switch to the SMARTDrive command in your AUTOEXEC.BAT file.
/V Instructs SMARTDrive to display status and error messages when it starts. (By default, SMARTDrive does not display any messages unless it encounters an error condition.) The /V switch cannot be used in conjunction with the /Q switch.
/Q Instructs SMARTDrive not to display status messages when it starts. (By default, SMARTDrive does not display status messages when loading, but does for most other operations.) If SMARTDrive encounters an error while starting, it displays an error message whether or not it was loaded with the /Q switch. The /Q switch cannot be used in conjunction with the /V switch.
/S Displays additional information about the status of SMARTDrive.
/E:ElementSize Specifies in bytes the amount of the cache that SMARTDrive moves at a time. Valid values are 1024, 2048, 4096, and 8192. The default value is 8192. The larger the value, the more conventional memory SMARTDrive uses.
/B:BufferSize Specifies in bytes the size of the read-ahead buffer. A read-ahead buffer is additional information that SMARTDrive reads when an application reads information from the hard disk. For example, if an application reads 512K of information from a file, SMARTDrive then reads the amount of information specified by BufferSize and saves it in memory. The next time the application needs to read information from that file, it can read it from memory instead. The default size of the read-ahead buffer is 16K (16384 bytes). Its value can be any multiple of ElementSize. The larger the value of BufferSize, the more conventional memory SMARTDrive uses.

See Also