On 8/6/2023 2:35 PM, Jerome Shidel via Freedos-user wrote:
First…
There seems to be a general misunderstanding that DOS only supports
80x25 columns. While it is possible that an extremely lazy programmer
would hard code for that resolution, most did not. Even back in the
early days the display could be in 40x25, 80x43, 80x50 and numerous
other text resolutions. Through the use of special text mode fonts,
most VGA cards could even support different font heights producing
very unusual display resolutions such as 80x20, 80x16, 40x22, etc.
Therefore it was always a bad idea to hard code support for a single
display resolution into software.
Sorry, Jerome, but that is all beside the point. The OP is not trying a
different text resolution, but is trying to force a graphics mode, which
will NEVER work with any basic DOS text mode program.
Yes, it is possible, at least on legacy hardware, to get text
resolutions other than 80x25 and 40x25 (as well as 80x43 on an EGA
adapter and 80x50 on a VGA adapter), but those are HIGHLY legacy
hardware depended, as they rely on directly manipulating the VGA
adapters sync registers.
I used to write and use a tool myself that could generate up to 132x60
character text screens, on the right VGA hardware.
HOWEVER, on a lot of newer video card/chips, this direct manipulation
doesn't work anymore, as those newer chips simply do not support the
sync of the video signal in the same way as undocumented ways of the
original VGA adapters allowed. On some, you will actually damage the
hardware, as you are generating out of bounds frequencies, on some,
simply nothing will happen, either no change or simply a turning of the
video signal, resulting in a black screen, from which only a cold boot
and subsequent re-initialization of the video hardware will recover from.
It will also no work on a lot of LCD/LED screens, which do no sync the
video signal like old CRT monitors did.
Ralf
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