Microsoft KB Archive/141368

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Article ID: 141368

Article Last Modified on 1/19/2007


  • Microsoft Windows Millennium Edition
  • Microsoft Windows 98 Second Edition
  • Microsoft Windows 98 Standard Edition
  • Microsoft Windows 95

This article was previously published under Q141368


When you run a program that accesses a CD-ROM drive, you may notice that the program is not performing optimally. You may notice slow data transfer in a business or reference program, or skipping or slow audio and video in a multimedia program.


This behavior can occur when the Supplemental Cache Size and Optimize Access Pattern For settings are not be set correctly for your CD-ROM drive.


To resolve this issue, follow these steps improve your CD-ROM drive's performance:

  1. Click Start, point to Settings, click Control Panel, and then double- click System.
  2. On the Performance tab, click File System.
  3. Click the CD-ROM tab.
  4. Move the Supplemental Cache Size slider to the right to allocate more random access memory (RAM) for caching data from the CD-ROM drive or to the left to allocate less RAM for caching data.

Note that many multimedia programs perform better with a smaller cache because these program tend not to reuse data.

  1. For reading continuous data, such as .avi files, use a higher setting in the Optimize Access Pattern For box. For reading random data, increase the Supplemental Cache Size setting and decrease the Optimize Access Pattern For setting.
  2. Click OK, and then click Close. When you are prompted to restart your computer, do so.

NOTE: If you are using real-mode drivers for your CD-ROM drive, these settings have no effect.


The supplemental cache is used to hold path table, directory, and file information. It is a passive cache holding data that has been accessed and may be accessed again.

The Optimize Access Pattern For setting is based on a 64K cache (single- speed read ahead plus 14K random access cache). This is incremented in 50K increments depending on the CD-ROM drive speed. It is an active buffer storing data initially read from the CD-ROM.

The default cache size is not based on the CD-ROM drive, but on the amount of RAM in the computer, as follows:

  • For computers with less than 8 MB of RAM, the default setting is single-speed read ahead cache (50K) + small random access cache (14K).
  • For computers with from 8 to 12 MB of RAM, the default setting is double-speed read ahead cache (100K) + medium random access cache (512K).
  • For computers with more than 12 MB of RAM, the default setting is quad-speed read ahead cache (200K) + large random access cache (1024K).

Keywords: kbenv kbfaq kbhardware kbprb KB141368