AOS/VS exploited the 8-ring protection architecture of the Eclipse MV hardware with ring 7 being the least privileged and ring 0 being the most privileged. The AOS/VS kernel ran in ring 0 and used ring-1 addresses for data structures related to virtual address translations. Ring 2 was unused and reserved for future use by the kernel. The Agent, which performed much of the system call validation for the AOS/VS kernel, as well as some I/O buffering and many compatibility functions, ran in ring 3 of each process. Ring 4 was used by various D.G. products such as the INFOS IIDBMS. Rings 5 and 6 were reserved for use by user programs but rarely used except for large software such as the MV/UX inner-ring emulator and Oracle which used ring 5. All user programs ran in ring 7. The AOS software was far more advanced than competing PDP-11 operating systems. 16-bit AOS applications ran natively under AOS/VS and AOS/VS II on the 32-bit Eclipse MV line. AOS/VS was the most commonly used DG software product, and included a command-line interpreter allowing for complex scripting, DUMP/LOAD, and other custom components. The 16-bit version of the CLI is famous for including an Easter egg taken directly from the Colossal Cave Adventure game. A user typing in the command "xyzzy" would get back a response from the CLI of "Nothing Happens". When a 32-bit version of the CLI became available under AOS/VS II, the same command instead reported "Twice As Much Happens". A modified version of System V.2 Unix called MV/UX hosted under AOS/VS was also available. A modified version of System V Unix called DG/UX was made for the Eclipse MV line and later the 88K and x86AViiON machines. The AOS and AOS/VS kernels were written entirely in assembly language. Almost all of the AOS and AOS/VS utilities included in the operating system releases were written in variants of the PL/I programming language. Initially, AOS/VS utilities closely tracked AOS source development. As AOS/VS matured, many DG-supplied utilities were rewritten to take advantage of the 32-bit address space and reduce dependencies on assembly language, often resulting in substantial increases in functionality, performance and reliability compared with their AOS ancestors.
Session
*** Atari S/W Development HCD1 / BATCH OUTPUT FILE ****
AOS/VS 3.07 / EXEC 3.07 19-JAN-84 10:11:01 QPRI=254 SEQ=31324 INPUT FILE -- :UDD:SYSTEMS:850:?031.CLI.004.JOB LIST FILE -- :QUEUE:NORDIN.LIST.31324 -------- LAST MESSAGE CHANGE 12-JAN-84 16:06:08 Atari S/W Development System HCD1 Backup schedule : Saturday 21-Jan-84 9:30-11:30am Refer to HELP *COMMANDS, HELP *PSEUDO, HELP, APHELP, and ?MHELP. Refer to DISP FUNC in SED for list of default function key commands. -------- LAST PREVIOUS LOGON 19-JAN-84 10:09:45
