QIC 40/80 Tape Drives Slow with Adaptec 154x Controller

• Microsoft Windows NT operating system version 3.1
• Microsoft Windows NT Advanced Server version 3.1

SYMPTOMS

After you configure an Adaptec 154xC or 154xCF SCSI controller for floppy controller support, data transfer on QIC 40/80 tape drives may be slow.

NOTE: If you are using an Adaptec 154xA or 154xB SCSI controller and the performance is slow, upgrade to the Adaptec 154xC or 154xCF and change the busontime/busofftime values, if necessary.

CAUSE

This problem occurs on ISA-based machines when devices that use floppy controllers contend for DMA time with devices that use SCSI controllers. EISA-based machines do not have this problem because they have a built-in DMA arbitrator circuit.

RESOLUTION

Download 1542CCFG.ZIP from Adaptec's BBS at (408) 945-7727. After you extract the files, follow these steps:

1. Boot your machine and press CTRL+A when the system is verifying and running the SCSI configuration. This allows you to run the SCSISELECT utility in the MS-DOS environment.

2. Select MS-DOS at the Windows NT flexboot option, or place an MS-DOS boot disk in drive A. Follow Step 1 again.

3. In conjunction with the utility, run C_CONFIG.EXE if you have an Adaptec 1542C or CF_CONFIG.EXE if you have an Adaptec 1542CF.

   NOTE: C_CONFIG.EXE and CF_CONFIG.EXE are available after extracting

            1542CCFG.ZIP.
   
   

4. In Advanced Configuration, set the values of:

         BusOnTime to 4 microseconds
         BusOffTime to 12 microseconds
   

5. Exit the utility program and restart your system.

STATUS

The product discussed here is manufactured by Adaptec, a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.