BUG: SCSI Scanners on Multiple Adapters Not Recognized

The information in this article applies to:

• Microsoft Windows NT Workstation version 3.50
• Microsoft Windows NT Server version 3.50
• Microsoft Windows NT Workstation version 3.51
• Microsoft Windows NT Server version 3.51

SYMPTOMS

On systems using SCSI scanners, if the scanners are placed on more than one SCSI adapter at the same time, some of the scanners will not be recognized by Windows NT. The first scanner, regardless of which adapter it is on, should always be recognized.

Consider a system with two SCSI adapters, with a SCSI scanner on each adapter. Only one scanner will be found on this system, and the order in which adapters are scanned is platform-dependent.

Note that there are no system event messages logged that indicate that this problem is occurring.

CAUSE

The SCSI scanner class driver (Scsiscan.sys) keeps a count of the scanner devices located during initialization. This count is incorrectly reset to zero each time a new adapter is searched. When a new device name is created for a scanner, it might conflict with a scanner device already created, so the new scanner is not usable.

RESOLUTION

As a temporary workaround, ensure that all scanners are on a single SCSI adapter. With this setup, all scanners should be identified and claimed.

STATUS

Microsoft has confirmed this to be a problem in the SCSISCAN driver. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.