XGA/1 or XGA/2 Video Adapter Cannot Play Full-Screen .AVI File

• Microsoft Windows 95

SYMPTOMS

When you start Windows 95 you do not see the Windows 95 logo screen, and you cannot play full-screen .AVI files.

CAUSE

The XGA/1 or XGA/2 video adapter that you are using does not support mode-X video. The Windows logo screen and full-screen .AVI files are displayed using mode X.

STATUS

This situation is most likely caused by design changes in Windows 95. Microsoft has confirmed that it is not caused by a problem in Windows 95. For more information about resolving this issue, contact the manufacturer of your video adapter.

MORE INFORMATION

With mode-13h video, the addressing of pixels is done in a linear fashion. That is, when you are accessing video memory with mode 13h, increasing a given address by one byte results in the address of the next pixel in sequence. While this type of addressing can be very effective for less complex tasks, it is not as useful for more complex graphics applications.

In particular, you can address only one video page using mode 13h. As a result, you can access only about 64K of video memory, which is not practical when you are programming for modern display adapters that typically have 256K or more of memory installed. To avoid this problem and other problems associated with mode 13h, programmers often use mode X instead. Mode X involves direct programming of the VGA registers, which allows for greater flexibility and the ability to address more memory.