#175149 /db4_info
26-SEP-90 12:11  
FILE: dBASE IV 1.1 Bulletin #2  
From: Steve
  To: ** ALL **

VIDEO MODE PROBLEM WITH AT&T AND OLIVETTI COMPUTERS

Screen display problems may be seen during the Installation and
running of dBASE IV on certain AT & T and Olivetti computers.
The problems occur most often when these machines have CGA cards
and specific BIOS versions.

During the installation of dBASE IV, the default video mode is
erroneously set to 43 lines.  However, since only 25 lines can be
displayed on this machine, the bottom 18 lines are not visible.
This means that during Install any messages that appear on the
bottom of the screen (e.g. "Press any key...") are not visible to
the user.

Similarly, within dBASE IV, at the dot prompt or in ASSIST, only
25 lines are visible on the screen and the bottom 18 lines are
not visible.

The machines against which the problem has been reported are:
AT & T 6300 with BIOS versions of 1.17 and 1.43, Olivetti M-21
and M-24 computers, and the Xerox 6060 with BIOS version 1.36.
The computer's BIOS version will display on the screen in the
upper left during power up.

This problem is related to a change in the method that dBASE uses
to check the current video mode and an inherently incorrect
setting of a byte in memory that describes the current video mode
as set by the ROM BIOS of these particular machines.

Consequently, a small program has been developed to switch this
byte to a value that correctly indicates the current video mode
(CGA) on these computers.  This program, FIXVID.COM is available
for downloading from the Ashton-Tate Bulletin Board.  The program
can be run daily from the AUTOEXEC.BAT file, or from a batch file
just prior to entering dBASE IV.

Alternatively, the following dBASE program run at the dot prompt
will create FIXVID.COM:


_pdriver="ASCII"
SET PRINTER TO FILE fixvid.COM
??? "{49}{192}{142}{216}{198}{6}{132}{4}{0}{195}"
SET PRINTER TO


If you desire to use this method to create FIXVID.COM, after a
successful installation from the dot prompt within dBASE IV,
first issue the command RUN CLS.  This will cause the video mode
to be reset during the current dBASE session.  After FIXVID has
been created, quit dBASE IV and run FIXVID from DOS.  Running
FIXVID from the AUTOEXEC.BAT file will cause it to be invoked
each time the computer is booted.  This will allow dBASE IV to
display properly every time it is run.

This program can also be created in DOS through the use of
DEBUG.COM.  After starting DEBUG, the following script can be
typed in:  (Note that commands are proceeded by the following
prompts: a dash/hyphen "-", a memory address "NNNN:NNNN", or a
colon ":")


C:>DEBUG
-A                         (You type "A")
24EC:0100 XOR AX,AX            (You type XOR AX,AX only!)
24EC:0102 MOV DS,AX
24EC:0104 MOV BYTE PTR [484],0
24EC:0109 RET
24EC:010A                      (simply press return here)
-RCX
CX 0000
:0A                   (You type zero, then A)
-N fixvid.COM
-W
Writing 000A bytes
-Q                    (Returns you to DOS)


When you return to DOS, you will have created the file
FIXVID.COM which can then be run by typing FIXVID.