Poor Performance from CD-ROM-Based Program

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     This article discusses a Beta release of a Microsoft
     product. The information in this article is provided as-is
     and is subject to change without notice.

     No formal product support is available from Microsoft for
     this Beta product. For information about obtaining support
     for a Beta release, please see the documentation included
     with the Beta product files, or check the Web location
     from which you downloaded the release.

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The information in this article applies to:

• Microsoft Windows 98
• Microsoft Windows 95

SYMPTOMS

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.

CAUSE

The Supplemental Cache Size and Optimize Access Pattern For settings may not be set correctly for your CD-ROM drive.

RESOLUTION

Try the following steps to improve the CD-ROM drive's performance:

1. In Control Panel, 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 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.

5. 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.

6. Click OK, and then click Close. When you are prompted to restart your computer, do so.

MORE INFORMATION

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).