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Problems attaching SCSI-2 devices to SCSI-3 adapter

This article was previously published under Q168094
This article has been archived. It is offered "as is" and will no longer be updated.
After you attach a 50-pin or Centronics SCSI-2 hard disk, scanner, tapeDrive, or other device to a 68-pin SCSI-3 interface, your computer may stopresponding or not respond when accessing SCSI bus. You may or may not seeany events in the event log indicating a problem.
Obtain a proper SCSI-2 to SCSI-3 conversion cable or terminator.
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 ahigh and a low control byte. When going from a SCSI-3 interface down to aSCSI- 2 device, the SCSI-3 high byte needs to be terminated while lettingthe low byte pass through (see Diagram 1). Most SCSI-3 to SCSI-2 cables donot have proper termination and need a special adapter for the high byte toterminate. Unless the documentation that comes with the conversion cablestates that it terminates the high byte, proper termination will not happenand 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:See "Connecting 8-Bit and 16-Bit Devices to an Adaptec Wide Host Adapter".

Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.
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Article ID: 168094 - Last Review: 01/10/2015 11:11:00 - Revision: 4.2

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

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