jcmorris@mwunix.mitre.org (Joe Morris) (05/29/91)
I've got a problem involving non-windows comm programs run from a DOS window in enhanced mode. So far Microsoft says that they haven't heard of it, so I'm posting this to the real world for suggestions... Symptom: in a cold-booted machine, CONFIG.SYS with nothing but HIMEM, SMARTDRV, and ANSI, no AUTOEXEC file, start Windows in enhanced mode. Select PROGRAM MANAGER -> MAIN -> DOS to get a full-screen DOS prompt. Issue the command MODE COM1:9600, then type the EXIT command to return to Windows. You may see part of the Windows screen rebuilt, but the screen flashes and you're left with a blank screen with bars where text should be. BIOS thinks that the screen is in mode 3 (normal EGA) but there's no text visible. Blindly typing "MODE CO80" restores the screen. When you look around you find that Windows is completely gone from the system. The amount of memory available for program execution is what you had before you started Windows. Other symptoms might be "merely" being dumped back to DOS with an apparently normal screen, or it might be the dreaded "Invalid COMMAND.COM, system halted" message. Whatever the symptoms they are completely repeatable. The problem is critically dependent on what is where in memory. I can change the symptoms by adding dummy TSR's or device drivers to change the memory available to Windows. The problem has been seen on IBM PS/2 and NEC PowerMate/386 systems with 4 and 6 MB of memory. I'm playing with an 8 MB Compaq but haven't found the right key to trigger it yet. The only thing I've found which prevents the failure is to lie to Windows in the [386enh] section of SYSTEM.INI and tell it that COM1 is something other than 3F8. None of the other comm settings have any visible effect. This problem originally was triggered by a new version of YTERM, but I later demonstrated it with MSKERMIT and then the DOS MODE command. Microsoft says that they have no reports of this type of failure, although some YTERM sites tell me that they've seen it. Does anyone in NetLand recognize the symptoms? If so, did you tell Microsoft? Suggestions? Help..... /Joe Morris