Microsoft KB Archive/67587

ANSI.SYS Causes Video to Lose Horizontal Sync in Some Modes PSS ID Number: Q67587 Article last modified on 07-14-1993 PSS database name: O_MSDOS

4.00 4.01

MS-DOS

Summary:

The ANSI.SYS console device driver supplied with Microsoft MS-DOS versions 4.0 and 4.01 can cause VGA video systems to lose horizontal synchronization following a video mode change.

More Information:

When using the SORTDEMO supplied with Microsoft QuickBasic, and MS-DOS 4.01 ANSI.SYS is enabled, the display loses horizontal synchronization. This problem can occur on both IBM VGA (Model 30) and Chips 82C451 VGA chip set. This problem does not occur on COMPAQ video systems.

This problem can also be duplicated by using the _settextrows function of the Microsoft C GRAPHICS Library as shown in the following C program:


 * 1) include 

main { _settextrows(43); }

It is possible, but not confirmed, that adding the /L switch to the ANSI.SYS DEVICE= line corrects the problem. This switch is documented in the README.TXT file supplied on the MS-DOS 4.0 disks.

Microsoft has confirmed this to be a problem in MS-DOS versions 4.0x. This problem does not occur in later versions of MS-DOS.

Additional reference words: 4.00 noupd

Copyright Microsoft Corporation 1993.