PC Hacks 100 Industrial-Strength Tips and Tools

< Day Day Up >

Hack 66 Speed Up Windows with VCACHE

If you absolutely must stick with Windows 9x or Me the least you can do is give your system this free performance-boosting tweak to your Windows disk cache.

The Windows operating system creates and maintains its own read-ahead disk-caching service to help speed things up, but Windows itself does not give you any direct control over VCACHE. Instead, you have to dig into the C:\WINDOWS\SYSTEM.INI file with a text editor to set the caching service to your liking.

When setting a value for disk caching, you have to balance the amount of RAM to be used for programs and data with the RAM set aside for disk caching. If a lot of RAM is assigned to disk caching, that leaves less for programs and data and Windows will use the swapfile more, which will slow things down. If you assign too little RAM for disk caching, disk operations may be a bit slower but Windows may use the swapfile less, thus keeping performance up a bit.

There is also another balancing act going on here: do you let Windows waste time looking in the cache for data that is not there, which can happen if the cache is too large, or give it less space to look through so it can get directly to the disk drive as quickly as possible? The best approach is to have just enough memory allocated for some caching benefit and not so much that we cheat our programs and Windows.

Fortunately most disk drives have between 256 KB and 8 MB of cache dedicated to data caching to and from the disk drive interface. So, as long as the IDE, SCSI, or SATA interface can keep up, the disk drive will not be a significant data bottleneck (beyond being hundreds of times slower than CPU and I/O bus speeds). With that in mind, you should not have to assign a lot of RAM to Windows disk caching.

Windows 98 has a known problem with VCACHE consuming all or nearly all available memory on systems with more than 512 MB of RAM, causing out-of-memory errors or crashes. Setting the parameters for VCACHE manually is the official fix for this problem.

To keep Windows from stealing too much RAM for VCACHE, you can add two lines to the SYSTEM.INI file to nail the disk caching down, following these steps:

I chose to give the cache only 256 KB of RAM because I've found that more is not always better. If you have a lot of RAM in your system, you may certainly use 512 or 1,024 KB, but you may not see a significant performance boost because of all of the overhead of Windows and drivers between the disk and the CPU.

Microsoft recommends that VCACHE not be set over 40 MB (40,000), which is a significantly high amount of RAM to leave for possible disk caching. At most, matching the amount of cache on your hard drive—256 KB to 8 MB—may be the best balance between RAM consumption and drive performance.

< Day Day Up >