Cannot Access CD-ROM Drive on Acer Pentium PCI using Cmd640x

This article was previously published under Q139987
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After you upgrade an Acer computer from an earlier version of Windows toWindows 95, the following problems may occur:
  • The CD-ROM drive is not detected.
  • 32-bit disk and file access is not available.
These symptoms may also occur when you upgrade an Acer 91.AA260 computerto Windows 98.
These problems can occur if the CD-ROM drive is connected to a CMD CSA-6400E PCI IDE controller. The Cmd640x.sys real-mode driver on Acercomputers is designed to work in Windows 3.1 and does not work inWindows 95.

If you use the CMD 6400 PCI controller protected-mode driver CMD CSA-6400E, 32-bit disk and file access is functional but the CD-ROM drive isnot detected.

If you use the CMD 6400 PCI controller real-mode driver Cmd640x.sys, theCD-ROM drive is detected, but 32-bit disk and file access is notavailable.

All Acer computer systems with a part number starting with 91.AA043 or91.AA260 using the CMD CSA-6400E PCI IDE controller and a Maxtor 7546AThard disk running Windows 95 exhibit this behavior.
To correct this problem, load the Windows 95 version of the CMD CSA-6400E PCI IDE driver. Download the self-extracting file Cmdwin95.exefrom Acer's FTP server (, or from Acer's World Wide Website ( For additionalinformation, please contact Acer Technical Support.

You may be able to resolve this issue using the following steps:
  1. Click Start, point to Settings, and then click Control Panel.
  2. Double-click System, and then click the Device Manager tab.
  3. Double-click Hard Disk Controllers, and then double-click CMD 640 Bus Master Controller.
  4. On the Settings tab, click Both IDE Channels Enabled in the Dual IDE Channel Settings box, click OK, and then click OK.


Article ID: 139987 - Last Review: 01/07/2015 06:15:51 - Revision: 1.2

Microsoft Windows 95, Microsoft Windows 98 Standard Edition

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