DOCUMENT:Q75095  17-DEC-2000  [msdos]
TITLE   :CLS Does Not Clear Screen on AT&T 6300
PRODUCT :Microsoft Disk Operating System
PROD/VER:MS-DOS:5.x,6.0,6.2,6.21,6.22
OPER/SYS:
KEYWORDS:

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - Microsoft MS-DOS operating system versions 5.0, 5.0a, 6.0, 6.2, 6.21, 6.22 
-------------------------------------------------------------------------------

SYMPTOMS
========

After starting an AT&T 6300, MS-DOS uses only one line of the screen to
display commands such as DIR, TREE, and so on; however, the startup information
remains on the screen even after issuing the CLS command. In the other cases,
the system will hang at the DOS prompt after pressing ENTER a few times.

WORKAROUND
==========

To work around this problem, add the following line to the CONFIG.SYS file, or
use the debug script listed below.

      device=ansi.sys /s

The same behavior occurs on AT&T 6310 machines.

MORE INFORMATION
================

The ANSI.SYS /S switch is an undocumented switch that will force the video to
display in 25-line mode. MS-DOS 5.0 or 6.0 relies on byte 40h:84h of the BIOS to
work in 43/30 line mode. The earlier version of MS-DOS did not use this byte.
The following is a short program to patch the BIOS area into having the 25
(actually 24, because it is is 0-based) value required for a CGA/MDA adapter.

At the DOS prompt, type "debug" (without the quotation marks).

You will then see the Debug prompt (a hyphen). Type the following, pressing ENTER
after each line:

Debug              User
Response           Input
--------           -----

C:\>               debug
-                  n patch.com
-                  a
xxxx:xxxx          mov ax,40
xxxx:xxxx          mov es,ax
xxxx:xxxx          es:
xxxx:xxxx          mov byte ptr [84],18
xxxx:xxxx          int 20
xxxx:xxxx          <press ENTER>
                   <press ENTER>
-                  r cx
:                  d
-                  w
-                  q

This will create PATCH.COM, a file you can execute from the command prompt. If
the problem is resolved, put an entry to execute the PATCH.COM file in the
AUTOEXEC.BAT file.

Additional query words: 6.22 boot ATT att6300 scroll scrolling 5.00 5.00a 6.00 6.20

======================================================================
Keywords          :  
Technology        : kbMSDOSSearch kbMSDOS621 kbMSDOS622 kbMSDOS620 kbMSDOS600 kbMSDOS500 kbMSDOS500a
Version           : MS-DOS:5.x,6.0,6.2,6.21,6.22

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 2000.