While rebooting, there is a 5-second window (while the dots appear in the bottom left) to hit [Ctrl]-[D] which puts you into DOS mode. If you miss the window, start over again.
These dots appear after a series of messages (NIC type, Bus type, Slot, BusNo, I/O base, Interrupt, Transceiver, Ethernet Address, and Packet Driver Interrupt). The place where the 5 periods are displayed are two lines below the Packet Driver Interrupt line.
Attached is a utility disk which makes the process a little easier. This disk allows you to exit to DOS directly on an Obsession II running VxWorks after performing a [Right-Shift]-[Tab]-[Tab]. It will also allow you to boot directly to DOS when powering up a processor. 6765.dosxdisk.exe
This disk is primarily intended for VxWorks Obsession systems (Version 4.3 and later). However, DOS exit on boot functionality is fully backward compatible with all released versions of Obsession II software, and all Obsession (I) software versions.
How It Works
This disk contains (3) DOS batch files. STARTUP.BAT, INSTALL.BAT, and DELBAT.BAT. The first two files mimic the filenames of the files on a software upgrade disk. On boot or restart, the Obsession II thinks these files are part of a software upgrade, so they are loaded before the Obsession executable. However, these two little files interrupt the boot process and cause a direct, but safe exit to DOS. It is a safe DOS exit because it runs the full AUTOEXEC.BAT file, unlike exiting with control-c. This means it is safe to run the Obsession executable without worrying about crashing as can happen with a control-c exit.
STARTUP.BAT is loaded by AUTOEXEC.BAT. STARTUP.BAT then renames the OBS.EXE file to TEMPOBS.EXE and copies INSTALL.BAT from the A drive to C:\ETC\OBS.BAT. Once that is done, the rest of the AUTOEXEC.BAT file executes and the file "obs" is called. Instead of launching the Obsession executable as intended, this runs the OBS.BAT file. The OBS.BAT file then renames TEMPOBS.EXE as OBS.EXE and then runs the batch file DELBAT.BAT. DELBAT.BAT deletes the OBS.BAT file, restoring the C drive to it's normalstate. DELBAT.BAT then outputs descriptions of some common Obsession DOS commands.
The only file modified by these batch files is the OBS.EXE executable. If Obsession fails to start up properly after use of this disk, check to see if the OBS.EXE is still named TEMPOBS.EXE. This could be caused by a disk error or a corrupt file on the disk. Type "ren tempobs.exe obs.exe" and hit enter to fix this problem. Also delete the file OBS.BAT if it is present in the c:\etc directory by typing "del obs.bat enter". The Obsession system should then function normally.