2500 SX/20  (250-4077)          Video Modes           Faxback Doc. # 1193

Note: Video Upgrade Part # MX-3750

Note: Refer to Faxback Doc. # 1194 for Main Logic Board Layout. The video 
circuitry for the Tandy 2500SX/20 is included on the main logic board.

This circuitry features:

* IBM VGA compatibility plus support for Super VGA modes with 132-column 
  text and both 800 x 600 and 1024 x 768 resolution graphics.
* Support for Version 1 of the VESA (Video Electronics Standard Association)
  Super VGA BIOS Extension specification.
* 256KB video memory (RAM), expandable to 512KB to support more extended VGA
  modes.
* A color palette of more than 262,000 possible colors.
* Compatibility with both monochrome and color, fixed and multiple-frequency
  monitors (including 8514/A-compatible monitors).

NOTE: The Video Chip Set is WD90C00.

Monitor and Software Compatibility:

The video circuitry is compatible with software written for the following
video standards on color or monochrome VGA analog monitors:

* VGA (Video Graphics Array)
* VESA Super VGA
* MCGA (Multi-Color Graphics Array)
* EGA (Enhanced Graphics Adapter)
* CGA (Color/Graphics Adapter)
* MDA (Monochrome Display Adapter)
* Hercules graphics (Hercules Graphics Card)

To emulate one of these video standards, use the vga.1024.exe utility on
MS-DOS Disk 2. Some Super VGA modes require application-specific drivers. 
Run vesa.exe on MS-DOS Disk 2 before your run an application that uses a
VESA-compatible driver.

Default Video Mode:

The video circuitry is in the VGA text mode when you turn on the computer. 
If your have a monochrome monitor (or no monitor connected at startup) and 
the VGA BIOS mode jumper is set to AT, the video default is monochrome text
mode.  Otherwise, 80-column color text mode is the default. The vga1023.exe
utility enables you to easily switch between color and monochrome modes.

Operation:

The video circuitry, in its default configuration, supports most application
software designed for VGA or EGA video support. Just turn on the computer, 
and install the application as instructed by the software manufacturer.

CAUTION: The video circuitry requires a VGA analog color or monochrome
monitor. Don not use any other type of monitor.

Connect the monitor to the 15-pin video connector on the back of the 
computer.  Refer to "Configuration Settings" in the "Installing Optional
Hardware" section for video-related jumper settings.

Configuring the Application Software:

Many application software packages include a program that prepares the
application for use with your particular hardware. you can reconfigure many
applications without re-installing them. You can also configure applications
during installation.l Follow the tips below for best results:

* To get the best-looking display, select the highest resolution mode
  available when you install your application software packages.
* Install your software for VGA or EGA if possible, so that the software 
  runs in the video circuitry's default configuration.
* If your software supports a video standard other than EGA or VGA, 
  configure it for the best standard. Run vga1024.exe and set the emulation 
  mode to match the program.
* If your software does not provide a VGA, a PS/2, or an EGA option and you
  use an RGB color analog monitor, install the software for color, if  
  available. This usually works with the video circuitry in default color 
  mode on a color monitor.
* Software that requires a certain video mapping may require you to set the
  video circuitry to color or monochrome text mode. For example, if the 
  video circuitry is set for color VGA text mode and your software requires
  monochrome text, you must use the vga1024.exe utility to switch modes.
* The default mapping is color for a color monitor and monochrome for a
  monochrome monitor.

Because some software packages are written specifically for hardware that is
not EGA-standard or VGA-standard, you might need to configure the video
circuitry to emulate the video adapter needed by the software. Use the
vga1023.exe utility as described in "Using Vga1024.exe." The tables in this
section list the video standards supported by the video circuitry and the
video modes and resolutions that are available under each standard.

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