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Windows 95 Help Files

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Adjusting Virtual Memory and Disk Cache in Windows 95
Windows 95 can dynamically manage both Virtual Memory (swap) and Disk Cache (vcache), thus making it run reasonably well in most all circumstances. Virtual Memory extends RAM by swapping data between RAM and the hard disk. Disk Cache speeds up hard disk access by storing info about recently accessed files. The Win95 vcache also caches CD ROM access and network traffic.

The default is to have Win95 manage both swap and vcache. Some people believe they can make things run better by tweaking the settings on their own, and you have that option in Win95. This may result in more free RAM and less swapping and resizing activity. I have not seen any reports of benchmark tests that indicate such adjustments actually increase performance.

You can adjust the swap space in the System Control Panel in Performance| Virtual Memory. Some people suggest setting a minimum of 20 to 30 MB and not setting a maximum. It's best to put the swap on a fast drive with lots of free space available. If you have Norton Utilities, you can use Speed Disk to put the swap file at the beginning of your HD and keep it defragmented.

You can set the VCACHE min and max in the system.ini file:

[vcache]
MinFileCache=4096
MaxFileCache=4096
In that example, you would get a fixed vcache of 4 MB. You can experiment with the numbers to see what works best for you.

If your hard disk is nearly full and you have chosen to set a fixed minimum size for swap, you run the risk of running out of disk space for temporary files. That can cause some applications to crash, especially during program installation, which can use lots of temporary disk space. If you set a fixed maximum size for swap, you run the risk of getting an out of memory message, which will also crash some unruly applications.

Here is a quote from the Win95 Resource Kit that may be helpful:

"Dynamic swap file and dynamic caching using VCACHE.

Windows 95 uses dynamic sizes for the virtual-memory swap file, the cache
for file and network access, and the CD-ROM cache.  Both the swap file and
cache sizes can grow or shrink, depending on the computers memory
configuration and the demand for memory from applications.  This relieves
users or administrators from having to change the cache parameters as new
memory or new applications are added.  Windows 95 can take advantage of
new memory automatically and expand or reduce the file and cache sizes
automatically based on demands when applications are loaded or unloaded. 
Also, the networking, disk, CD-ROM, and paging caches are integrated and
will scale as more memory is added to the computer. For more information,
see Optimizing the Swap File and Optimizing File System Performance."

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Send comments to: dwomble@cmb.biosci.wayne.edu

Copyright © 1997, David D. Womble.