KB168094 - Problems attaching SCSI-2 devices to SCSI-3 adapter

Article ID: 168094

Article Last Modified on 10/30/2006

Microsoft Windows 2000 Server
Microsoft Windows 2000 Professional Edition
Microsoft Windows NT Workstation 3.51
Microsoft Windows NT Workstation 4.0 Developer Edition
Microsoft Windows NT Server 3.51
Microsoft Windows NT Server 4.0 Standard Edition

This article was previously published under Q168094

SYMPTOMS

After you attach a 50-pin or Centronics SCSI-2 hard disk, scanner, tape Drive, or other device to a 68-pin SCSI-3 interface, your computer may stop responding or not respond when accessing SCSI bus. You may or may not see any events in the event log indicating a problem.

RESOLUTION

Obtain a proper SCSI-2 to SCSI-3 conversion cable or terminator.

MORE INFORMATION

For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

101352 Properly Connecting SCSI Devices to Windows NT

A SCSI-2 device uses a low control byte, but SCSI-3 devices have both a high and a low control byte. When going from a SCSI-3 interface down to a SCSI- 2 device, the SCSI-3 high byte needs to be terminated while letting the low byte pass through (see Diagram 1). Most SCSI-3 to SCSI-2 cables do not have proper termination and need a special adapter for the high byte to terminate. Unless the documentation that comes with the conversion cable states that it terminates the high byte, proper termination will not happen and possible data corruption can occur.

Diagram 1:

           SCSI-3 (68-Pin)                               SCSI-2 (50-Pin)

             High Byte            |------------------|
          ------------------------| Terminated       |
                                  |                  |
             Low Byte             |                  |    Low Byte
          -----------------------------------------------------------------
                                  |------------------|

For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:

154690 How to troubleshoot event ID 9, event ID 11, and event ID 15 error messages

193242 Windows Hangs at Logo Screen After Attaching External Device

You can also visit the following Adaptec Web site:

http://www.adaptec.com/worldwide/support/supporteditorial.jsp?supportCat=%2FProduct&cat=%2FTechnology&prodkey=8_and_16_bit_devices

See "Connecting 8-Bit and 16-Bit Devices to an Adaptec Wide Host Adapter".

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