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Starts the Fastopen program, which improves performance on computers with large directories. Fastopen decreases the amount of time that it takes to open frequently used files. Do not use this command when Windows is running.

Fastopen tracks the location of files on a hard disk and stores the information in memory for fast access.

Warning: To avoid losing data, do not run a defragmentation program such as Microsoft Defragmenter while FASTOPEN.EXE is loaded.


FASTOPEN drive:[[=]n,[m]] [drive:[[=]n,[m][...]] [/X]

drive: (v3.30)
Specifies a hard disk drive for which you want Fastopen to track the opening of files.
n (v3.30)
Specifies the number of files Fastopen can work with at the same time. Valid values for n are in the range 10 through 999. The default value is 10 (or 48?).
m (v4.0)
Allocates storage for file "extents" (FAT chains). It can range from 1 to 999. When omitted, this feature is not provided. As a general rule you may want to set m to about 4 times the value of n.

/X (v4.0)
Creates the name cache in expanded memory instead of in conventional memory. The name cache is an area of memory in which the operating system stores (caches) the locations and names of the files that you open. This cache conforms to version 4.0 of the Lotus/Intel/Microsoft Expanded Memory Specification (LIM EMS).



How Fastopen tracks information

Every time you open a file, Fastopen records its name and location in the name cache. If you later reopen a file recorded by Fastopen, the access time is greatly reduced.

Limits on using Fastopen

Fastopen works only on hard disks and does not work over a network. You can use Fastopen with as many as 24 hard-disk partitions at one time. For each partition, Fastopen can track the number of files specified by the n parameter. The maximum number of files that Fastopen can track on all partitions is 999.

You cannot run more than one copy of Fastopen at the same time. If you want to change the Fastopen settings, you must restart the operating system.

You should not use the Fastopen command from DOS Shell, because doing so can lock up your machine.

Memory requirements for Fastopen

Fastopen requires approximately 48 bytes of memory for each file that it tracks.

Adding the FASTOPEN command to your CONFIG.SYS file

You can add a Fastopen command to your CONFIG.SYS file by using the INSTALL command. Use this technique when you do not want to start Fastopen from the operating system command-line or from your AUTOEXEC.BAT file.


If you want to track the location of as many as 100 files on drive C:




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Windows NT