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September 1, 1997

Setting Win95 for performance can slow you down

It's often useful to tweak Windows 95 settings to get better performance for your system. In at least one case, however, changing a specific setting could decrease your performance rather than improve it.

This problem affects the dialog box that determines Win95's "Typical Use of This Machine." You reach this dialog box by clicking Start, Settings, Control Panel, then running the System applet, clicking the Performance tab, and clicking the File System button. Once there, your choices are Desktop Computer, Mobile or Docking System (for a laptop), and Network Server.

The three choices that are offered primarily determine how much RAM Win95 will use for a name cache. This cache is searched by Win95 for file names that have recently been used. Selecting Mobile or Docking System sets this cache to 4KB of RAM. Desktop Computer sets it to 8KB, and Network Server sets it to 16KB.

Reader Jeff Schneider, from Middleton, Wis., reasoned that with 32MB of RAM, his desktop PC had plenty of memory to afford a larger cache, so he changed his setting from a Desktop Computer to a Network Server. He was surprised, though, to find that his disk performance became worse rather than better.

The reason for this is that Microsoft inadvertently reversed two values in the Registry that define NameCache and another setting, PathCache, which caches 16, 32, or 64 directory paths.

When you change to a laptop or server setting, the wrong values are copied, which slows down your system.

This problem has been corrected in Windows 95B. If you have Windows 95 or 95A, you should take the corrective steps below if you use the Mobile or Server setting. The Desktop Computer setting uses default values and does not need to be corrected. If you don't know whether you have Win95B, your current version is shown in the General tab of the System dialog box.

  • Step 1. Because this fix edits your Registry, you should first back up the Registry files, User.dat and System.dat, which are hidden files in your Windows folder.

  • Step 2. Run RegEdit.exe. Find the following Registry key: Hkey_Local_Machine\Software\Microsoft\Windows\CurrentVersion\FS Templates. Select the Mobile or Server folder beneath this key.

  • Step 3. To fix the Mobile profile, right-click the NameCache and PathCache keys in the right pane, click Modify, then change their values to the following hexadecimal values.

    NameCache 51 01 00 00
    PathCache 10 00 00 00

    To fix the Server setting, modify NameCache and PathCache.

    NameCache a9 0a 00 00
    PathCache 40 00 00 00

  • Step 4. Exit RegEdit. In the System applet, click the File System button on the Performance tab. Select the profile you wish to use, for example, Mobile or Server.

This will write the correct values to another Registry key: Hkey_Local_Machine\System\CurrentControlSet\Control\File System.

Microsoft has acknowledged the problem. A description of it can be found at

Brian Livingston is the co-author of Windows 95 Secrets and four other Windows books (IDG Books). Send tips to or fax: (206) 282-1248.

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Copyright © 1997 by InfoWorld Publishing Company


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