At general availability OS/2 Version 2.0 provides the most complete support for video systems which provide VGA resolution. This is the only resolution supported for "seamless" WIN-OS/2 sessions at this time and if using "seamless" WIN-OS/2 on a particular system, the Presentation Manager desktop must be configured to use this resolution even if the display hardware is capable of higher resolution output.
OS/2 V2.0 provides support for devices with lower resolutions than VGA, namely CGA and EGA, for all types of sessions except "seamless" WIN-OS/2. Use of CGA for Presentation Manager is not recommended.
Devices with resolutions above VGA (640x480, 16 colors) are known as Super VGA (SVGA). The OS/2 installation process will detect display systems capable of running in SVGA mode. However, because of the wide variety of display systems currently available that fall into this category, full support is not provided.
Support is provided for 8514 and XGA display systems and drivers for Presentation Manager and WIN-OS/2 full-screen sessions will be installed during system installation. All other SVGA display systems will be supported in VGA mode. Systems with 8514 and XGA display hardware can also run in VGA mode.
Support however is provided to allow DOS full-screen and WIN-OS/2 full-screen sessions to use the display system in SVGA mode even though Presentation Manager is using it as a VGA device. A base video device handler (VDH) is provided which permits switching the display system between VGA and an SVGA mode. The list of video modes currently supported is:
SVGA support is enabled by:
SET VIO_VGA=DEVICE(BVHVGA,BVHSVGA)
From a DOS full-screen command prompt issue the command:
SVGA ON
Executing this program will result in a file called SVGADATA.PMI being created in the OS2 directory. This file contains the information about the video modes supported by the video adapter present in the system.
This file also serves a flag to say that SVGA mode is enabled in the system. The SVGA support is only active once the SVGA program has been run. SVGA VDHs will run in VGA mode if the SVGADATA.PMI file is not present.
This substitution provides support for DOS full-screen sessions to run in SVGA mode. The VVGA.SYS virtual VDH is replaced by VSVGA.SYS by changing the DEVICE statement in the CONFIG.SYS to read:
DEVICE=x:\OS2\MDOS\VSVGA.SYS
where x = the drive letter of the system partition
If a Windows V3.0 driver is available for the adapter, this should work
under OS/2 V2.0. Update the "display.drv=" line in the SYSTEM.INI file in
the \OS2\MDOS\WINOS2 directory to point to the new driver. The DEVICE statement
for the video driver in the CONFIG.SYS also needs to be changed.
To disable SVGA support run the SVGA.EXE program with the OFF parameter:
SVGA OFF
Changing DOS settings may rectify problems experienced when running with SVGA enabled:
Some manufacturers of SVGA hardware are working to develop OS/2 V2.0 video device drivers that will support Presentation Manager. It is advisable to check with the hardware supplier about the availability of drivers for a particular video subsystem. Information will also be posted on OS/2 bulletin boards and these can be checked for the latest information.