Dear SCO Customer, The enclosed Support Level Supplement (SLS) xnx170 corrects problems with installing a second Adaptec SCSI host adapter with SCO XENIX 386 Operating System Release 2.3.2 for computers based on Micro Channel Architecture (MCA). These problems caused mkdev hd to fail when trying to access the first disk on the second adapter. To install SLS xnx170, log in as "root" and type: /etc/install The installation will update the Adaptec drivers and relink the kernel. You will then need to run the following commands in order to install the new XENIX kernel as the default: cd /usr/sys/conf ./hdinstall Once the installation is complete the system should be rebooted off the new XENIX kernel. To reboot your system, enter the command: /etc/shutdown It should then be possible to install the disks on the second SCSI host adapter. To install a disk on a second SCSI host adapter, jumper the disk to be SCSI ID 0 on the second adapter. Once the disk is installed, issue the command: mkdev hd 0 1 In the above command, 0 refers to the SCSI ID and 1 refers to the second adapter. Please note that there are a number of configuration issues to be aware of when installing a second SCSI host adapter. The first adapter must be in a higher priority slot number than the second. Also, only the first card may have the BIOS enabled. The second card must have a lower base address than the first and should be configured to use interrupt vector 10 (the first adapter is configured for interrupt vector 15). There are 6 addresses available for use with the 1640 SCSI host adapter: 0x330 0x230 0x130 - with/without the BIOS enabled 0x334 0x234 0x134 - with BIOS disabled Normally, 0x330 would be used for the first SCSI host adapter and 0x230 for the second SCSI host adapter. If you have any questions, please call our SCO Customer Services Department at (800) 347-4381. SCO Customer Service is available Monday through Friday, 6:00 A.M. to 5:00 P.M., Pacific Time. We appreciate your business. SCO Support Services