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Index > OS Construction > How does Linux set it's high res text mode?

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rnop



Joined: 27 Jun 2010
Posts: 3
rnop
For bootsector use
Quote:

xor ax, ax
mov al, 0Dh
int 10h
Post 27 Jun 2010, 18:50
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rnop



Joined: 27 Jun 2010
Posts: 3
rnop
basically set a standard reasonabily safe graphics mode with the bios - something that is supported by most manufacturers; your kernel can then load proper drivers and init the card later on correctly after probing tons of code...
Post 27 Jun 2010, 18:52
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dakoder



Joined: 30 Jun 2010
Posts: 7
Location: Oxfordshire, UK
dakoder
mov eax,0x1112
int 0x10

This BIOS call work for me giving 80x48 mode 3 text it just doubles the scanlines and therefore has a much higher screen refresh update to a vesa mode.


Graham
Post 30 Jun 2010, 22:37
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baldr



Joined: 19 Mar 2008
Posts: 1651
baldr
dakoder,

80×50, perhaps (80×43 on EGA)? It doesn't double anything, just loads 8×8 character generator and reprograms videocontroller to accommodate changed character cell height.

In the similar way one can reprogram VGA to use 480 scan lines in text mode (instead of regular 400) and achieve 80×30 (80×60 if 8×8 chargen is used) resolution text mode.
Post 01 Jul 2010, 00:05
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dakoder



Joined: 30 Jun 2010
Posts: 7
Location: Oxfordshire, UK
dakoder
baldr wrote:
dakoder,

80×50, perhaps (80×43 on EGA)? It doesn't double anything, just loads 8×8 character generator and reprograms videocontroller to accommodate changed character cell height.

In the similar way one can reprogram VGA to use 480 scan lines in text mode (instead of regular 400) and achieve 80×30 (80×60 if 8×8 chargen is used) resolution text mode.

yeah EGA. as you say VGA just changed the font.

graham
Post 01 Jul 2010, 13:57
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edfed



Joined: 20 Feb 2006
Posts: 4240
Location: 2018
edfed
it is possible to achieve a very high text resolution with frame buffer.
frame buffer is the vesa double buffer for graphic mode.
using a graphic font, but emulating a text mode.

it lets linux print a picture behind the console, or add many graphical effects to an apparent text mode.
for exemple, using 1024*768 with a 8*8 font will give a text resolution of:
1024/8 * 768/16 = 128 * 96.

it is many more than 80*25 text mode.

i use a 8*5 (9*6) fixed font, in 1024*768, it can give a text resolution of 170*85.

the modes numbers for vesa text modes:

Code:
mode    columns   rows
108h       80      60
109h      132      25
10ah      132      43
10bh      132      50
10ch      132      60                  
Post 01 Jul 2010, 23:51
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