ConcurrentDOS 386 + GEMVDI, VGA display issue.

HOST : Centos 7.7.1908
QEMU version : 2.10.1
GUEST : Concurrent DOS version 3.01
GEMS version : ?

Hi all,

I have an issue on a GEM environnement when I switch from GEM window to DOS window, by pressing ctrl2, then ctrl1 to switch back to the GEM window (cf: attached files).
The issue is not present of course when the program is started on a native CDOS environnement, only occurs when it is virtualized in QEMU.

Process:
   - After starting the CDOS img with qemu, a software is started in windows 1, with selectionnable menus.
   - One menu call this function: gemvdi /m=31 -g:anwedi, wich start a graphical exe, showed on the Screen_before_switch.png img.
- Then press ctrl+2 (handled by CDOS to switch windows), and then ctrl+1 to go back to the graphical software.
   - Now the display is as you see it in the Screen_after_switch.png.

QEMU is launched with this command:

qemu-system-i386 -hda img.raw -m 8

I tried using different -vga options available (cirrus, vmware, virtio), with no success. The other vga options didn’t allow me to launch qemu at all.

I also tried different -display options (sdl, curses, gtk, vnc), same result.
I tried with -m 16, -m 32, no success.

I tried on a VirtualBox vm, using same CDOS image, and the problem doesn’t appear. It works fine. The difference I can see is the “graphic controller” used in virtual box display parameters, set to VBOXVGA. But as stated before, the -vga vmware, is not working.

Thank you for your help,

Best regards

From:	LE LIEGARD, Stephane
Subject:	ConcurrentDOS 386 + GEMVDI, VGA display issue.
Date:	Wed, 30 Sep 2020 15:54:43 +0000