Dear SCO Customer, The enclosed Support Level Supplement (SLS) xnx339c contains modified kernel modules that address the six issues listed below. (1) Bus corruption and kernel PANIC if: (A) A driver is configured at spl7 on the second PIC; (B) The same driver is being used under heavy interrupt load; (C) DMA is being used. (2) Drivers that make use of the secondary PIC by using IRQ 30 through 37 octal, or 24 through 31 decimal, may have the interrupt blocked until the SPL in the kernel is at level 0 (SCO XENIX 386 Operating System Release 2.3.4 specific). Under heavy load this may result in data loss for non-intelligent serial cards that are attached to the second PIC. There are two PICs on a typical PC platform. The diagram below shows the number of the IRQ and where they are assigned. Please note that, on your system, not all IRQ's may be used. PIC 1 PIC 2 +-----+ CPU <---| 0 |-- clock octal decimal | 1 |-- keyboard +--------------+ | 2 |<----------------| 30 24 |-- | 3 |-- tty2a | 31 25 |-- tape/net | 4 |-- tty1a | 32 26 |-- | 5 |-- lp2 or tape | 33 27 |-- serial | 6 |-- floppy | 34 28 |-- serial | 7 |-- lp0 or lp1 | 35 29 |-- FPU +-----+ | 36 30 |-- hdisk | 37 31 |-- hdisk/scsi +--------------+ (3) Under SCO XENIX Release 2.3.4 386 GT, the use of DMA Channel 3 will fail unless the kernel has been modified with adb(CP), as instructed in the SCO XENIX System V Operating System Release Notes dated "12 August 1991." Previous releases of the Release Notes will not have this information. The adb patch was: /etc/_fst -w /xenix dma_param+e ?w c033 dma_enable+d ?w c033 dma_resid+d ?w c033 \$q In addition, the Release Notes ensure that the above adb patch is applied each time you relink the kernel by adding the following lines to the bottom of the file /usr/sys/conf/hdinstall: /etc/_fst -w /xenix << EOF dma_param+e ?w c033 dma_enable+d ?w c033 dma_resid+d ?w c033 \$q EOF NOTE: This patch is not needed if SLS xnx339c is installed. SLS xnx339c will test for the presence of this adb patch in /usr/sys/conf/hdinstall. If the patch is detected, the installation of SLS xnx339c will abort and will not install until you delete the above adb patch from /usr/sys/conf/hdinstall. (4) File system corruption in the form of unreferenced files. (5) Shared memory problems. For example, as found in SCO uniPATH SNA-3270 Release 2.1. (6) Kernel/machine hangs during boot or installation due to spurious interrupts. NOTE: Item 1 and 2 above would seem to conflict. The kernel was changed in SCO XENIX Release 2.3.4 to behave as in item 2 to prevent the possibility of a panic listed in item 1. This SLS provides a correct solution to both problems. INSTALLATION: Before attempting to install this SLS, you must be running one of the following releases: SCO XENIX 386 Operating System Release 2.3.2 with xnx155 SCO XENIX 386 Operating System Release 2.3.2 with xnx296 SCO XENIX 386 Operating System Release 2.3.4 Note: Support Level Supplements xnx155 and xnx296 apply to SCO XENIX 386 Operating System Release 2.3.2 only. Each will upgrade the system from Release 2.3.2 to Release 2.3.3. SLS xnx339c will not install on Release 2.3.2 unless SLS xnx155 or SLS xnx296 have been installed. To verify the correct release of the operating system look at the boot screen or use the command: uname -r from the shell prompt. It should respond with either 2.3.3 or 2.3.4. The LINK kit must be installed; this can be verified with custom(ADM). (1) From the "#" prompt, type "custom" followed by . (2) Select option "1" from the custom(ADM) menu to select "Operating System". (3) Select option "3" from the custom menu to "List the available packages". (4) The "LINK" package must have a "yes" beside it. Next you need to be in single-user mode. Please follow the instructions below to install SLS xnx339c. (1) From the "#" prompt, type "custom" followed by . (2) Select option 4 from the custom(ADM) menu to "Add a Supported Product". (3) Insert the floppy when prompted and press . (4) Answer "y" followed by to continue the installation. (5) Select option "1" from the custom menu to "Install one or more packages". (6) Enter "all" followed by . (7) Press again since the floppy is already in the drive. (8) Answer "y" to the prompt "Do you want this kernel to boot by default (y/n)?" and press . (9) Select "q" to quit from the custom(ADM) menu. (10) Now remove the floppy from the drive. (11) Reboot the system with the reboot command: "reboot " 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