ULTRIX SCSI/CAM Architecture Release Notes and Installation Instructions

This document provides Release Notes and Installation Instructions for the ULTRIX SCSI/CAM Architecture (S/CA) Version 1.0 software, released in May 1992 by Digital Equipment Corporation. It is intended for individuals responsible for installing, managing, maintaining, and developing for S/CA on ULTRIX RISC Version 4.2A or higher systems, supporting various DECstation and DECsystem 5000 series processors. The Q-bus SCSI controller (KZQSA) for the DECstation 5500 is not supported.

Key Information and Release Notes:

• Architectural Change: The CAM subsystem completely replaces older SCSI device drivers. It provides standard support for Disk (rz#), CDROM/Audio (rz#), and Tape (tz#) devices.
• Third-Party Device Support: Includes information on attaching and installing third-party SCSI devices and drivers. CAM error logging handles large data structures by reporting errors and skipping entries.

• System Behavior:

  • During boot, CAM uses a 2-second polled timer for SCSI bus probing as system timers are not yet enabled.
  • A known issue exists where the User Agent driver can cause processes to hang due to interaction with the Virtual Memory subsystem if allocated buffers share pages. A workaround using malloc_palign and free_palign from uagt_lib.c for page-aligned buffers is provided.

• Device-Specific Issues:

  • RRD40 CDROM: Can hang the SCSI bus if a Bus Device Reset is issued, requiring a power cycle to resolve.
  • TLZ04 and TZ30 Tape: A Bus Device Reset is sent during device attachment due to a hardware problem, producing an informational message.
  • TZ85 Tape: The file command reports "unspecified density"; the tapex utility may report negative or smaller capacity. The dump utility requires specific density (42500) and length (57600) parameters for optimal use. Capacity reductions (20-85%) may occur for dump, cpio, dd, tar, and ltf utilities if default block sizes are used; specifying block sizes in multiples of 4 KBytes is recommended for dd, tar, and ltf.

• Device Mapping: The major/minor device number mapping for RZ (disk) and TZ (tape) devices used by S/CA differs from the /dev directory, but CAM drivers correctly map these to kernel entry points.

• Data Transfer: Odd-byte transfers on DS5000_100 systems return an extra 0xFF byte, but the correct byte count is indicated by the CAM Control Block (CCB).
• Removable Disks: The PREVENT MEDIUM REMOVAL command on opening a removable disk (like RRD42) can cause I/O errors if an EJECT command was previously issued. Workarounds involve issuing ALLOW MEDIUM REMOVAL or modifying kernel flags (SZ_PREV_ALLOW in cam_data.c).
• Utilities:
  • The cam_report utility provides supplemental SCSI/CAM error information to the uerf utility (note excess tab characters in log output).
  • Updated mt(1) (magnetic tape manipulation) and crash(8) (system image examination) reference pages are included. A new crash utility is part of the S/CA software, replacing the ULTRIX 4.2A version.

Installation Instructions (High-Level):

The installation process involves removing any existing CAM software subsets, loading the S/CA media (tape or CDROM), verifying sufficient disk space (approx. 1.7 MB), running the setld utility to install the CAM Kernel Configuration Files and CAM Base System Files, executing /etc/doconfig to configure the system, saving the old kernel, and renaming the newly built CAM-enabled kernel to vmunix before a system reboot. No manual configuration file changes are needed for the kernel build.