This page is written to show the effect of setting [vcache] in c:\windows\system.ini.
(A) Without [vcache] setting in system.ini
(B) With [vcache] setting in system.ini to limit the virtual cache/disk cache to 4096 Kbytes.
(A) Without any [vcache] setting in system.ini:
Through compressing a file - 00000037.dat - with size of 45,873,664 bytes, the physical RAM is filled with the cache of the file after the compression.
1% of Compression -
25% of Compression -
50% of Compression -
75% of Compression -
Compression completed -
As you can see, the free physical RAM was getting fewer and fewer until zero, while the swap file was getting larger at the same time. It's because Windows 9x uses as much RAM as possible to cache the files on disk, for faster respond time for same files in the future. It is a disaster for subsequent programs which are running other files, since they have to use swap file on harddisk to simulate physical RAM, and those files can't be cached since no free physical RAM left.
In order to limit the size of disk cache, [vcache] in system.ini must be set.
(B) With [vcache] setting in system.ini:
With [vcache] set to 4096 kbytes, the result is as following:
(Note: the old 00000037.zip was deleted, and the Windows was restarted)
1% of Compression -
25% of Compression -
50% of Compression -
75% of Compression -
Compression completed -
As you can see, the free physical RAM was always larger than 19 Mbytes, and the swap file was smaller than 5 Mbytes. By limiting disk cache/virtual cache to 4 Mbytes, the physical RAM is freed to be used by other programs. Thus, those programs can run faster in physical RAM rather than in harddisk's swap file. The Windows 9x's default disk cache setting is only benefit for those systems which have larger physical RAM, such as systems with more than 128 Mbytes RAM, AND those users who are using few programs repeatedly during same Windows' session.
In conclusion, we have to tweak Windows 9x's virtual cache's setting in order to get better program performance (but not necessary loading speed of programs) if we have less than 64 Mbytes physical RAM. The best utility I've ever used is "Cacheman" written by Thomas Reimann, whose homepage is http://members.xoom.com/ultimatum/cacheman.htm. The program is the one I showed on the right side of above pictures.
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