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How can I change DOS text screen mode permanently via SVGA

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First post, by tonychen

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I want to change the text mode to 800 x 600 or higher permanently, so I can see more lines when using edit, pwb, qbasic, or other tools
I use debug.exe to write "ax, 420F; bx, 10A; int 10h", and execute by "P" step by step. The program ends, but the screen does not change

I do not understand the VBE, I roughly write down the following process.
1. Install SVGA BIOS (univbe, sisvbe...)
2. Call the ASM program mentioned above
3. The text mode will be changed

Is there anything I misunderstood? Or, SVGA mode can only be set by the running program? Not by the DOS-shell?
Even though the current text mode is 800x600, when running edit.com, will it auto change to 320x200 or 640x480?
When quitting edit.com, it changes back to 800x600?

Reply 1 of 3, by weedeewee

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I recall in the olden days ANSI.SYS was loaded in config.sys and
MODE CO80,50 was used to get more lines on screen.
on some videocards you could even use MODE CON: COLS=132 LINES=50 or LINES=43 to get even more screen text mode real estate.
downside is that this did not always work with every text mode program. Some software just reset the video text mode back to 80x25.

unsure if ANSI.SYS had to be loaded or not to use the mode commands. Try it without first. 😀

fyi, This was in plain msdos and early plain W9x dos.

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Reply 2 of 3, by bakemono

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You can change the screen mode of the DOS command prompt, but it does not affect EDIT or QBASIC. Those seem to only support two modes at most, which are usually 80x25 and 80x50. (Presumably, on an EGA card you get 80x43 instead of 80x50.)

With the original BIOS INT $10 API, you load AH with 0 and AL with the mode number. With the VESA INT $10 API, you load AX with $4F02 and BX with the mode number.

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Reply 3 of 3, by BloodyCactus

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I have two utils to change your screen lines if you need 28 or 50

https://bloodycactus.com/files/28line.zip
https://bloodycactus.com/files/50line.zip

for 132x43 to work (which your attemping), after you enter 'P', and nothing happens,look at AX, if it sayts 014F, means its failed. if its 004F, it succeeded.
if AX = 4f02, then you dont have VESA support in your bios.

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