1 .. include:: <isonum.txt>
2
3 =================================
4 Video Mode Selection Support 2.13
5 =================================
6
7 :Copyright: |copy| 1995--1999 Martin Mares, <mj
8
9 Intro
10 ~~~~~
11
12 This small document describes the "Video Mode
13 allows the use of various special video modes
14 to usage of the BIOS, the selection is limited
15 kernel decompression starts) and works only on
16 booted through BIOS firmware (as opposed to th
17
18 .. note::
19
20 Short intro for the impatient: Just use vga
21 enter ``scan`` on the video mode prompt, pi
22 remember its mode ID (the four-digit hexade
23 set the vga parameter to this number (conve
24
25 The video mode to be used is selected by a ker
26 specified in the kernel Makefile (the SVGA_MOD
27 option of LILO (or some other boot loader you
28 (present in standard Linux utility packages).
29 of this parameter::
30
31 NORMAL_VGA - Standard 80x25 mode available
32
33 EXTENDED_VGA - Standard 8-pixel font mode:
34
35 ASK_VGA - Display a video mode menu upon st
36
37 0..35 - Menu item number (when you have use
38 modes available on your adapter, you can
39 to use). 0..9 correspond to "0".."9", 10
40 mode list displayed may vary as the kern
41 modes are listed in a "first detected --
42 better to use absolute mode numbers inst
43
44 0x.... - Hexadecimal video mode ID (also di
45 for exact meaning of the ID). Warning: L
46 hexadecimal numbers -- you have to conve
47
48 Menu
49 ~~~~
50
51 The ASK_VGA mode causes the kernel to offer a
52 bootup. It displays a "Press <RETURN> to see v
53 to continue or wait 30 secs" message. If you p
54 menu, if you press <SPACE> or wait 30 seconds,
55 the standard 80x25 mode.
56
57 The menu looks like::
58
59 Video adapter: <name-of-detected-video
60 Mode: COLSxROWS:
61 0 0F00 80x25
62 1 0F01 80x50
63 2 0F02 80x43
64 3 0F03 80x26
65 ....
66 Enter mode number or ``scan``: <flashi
67
68 <name-of-detected-video-adapter> tells what vi
69 -- it's either a generic adapter name (MDA, CG
70 with VESA-compliant BIOS]) or a chipset name (
71 of chipsets is turned off by default as it's i
72 absolutely insane PC design.
73
74 "0 0F00 80x25" means that the first menu ite
75 from "0" to "9" and from "a" to "z") is a 80x2
76 next section for a description of mode IDs).
77
78 <flashing-cursor-here> encourages you to enter
79 you wish to set and press <RETURN>. If the com
80 "Unknown mode ID", it is trying to tell you th
81 a mode. It's also possible to press only <RETU
82
83 The mode list usually contains a few basic mod
84 case your chipset has been detected, some chip
85 well (some of these might be missing or unusab
86 BIOSes are often shipped with the same card an
87 on the VGA BIOS).
88
89 The modes displayed on the menu are partially
90 the standard modes (80x25 and 80x50) followed
91 80x43), local modes (if the local modes featur
92 finally SVGA modes for the auto-detected adapt
93
94 If you are not happy with the mode list offere
95 is able to do more), you can enter "scan" inst
96 program will try to ask the BIOS for all possi
97 what happens then. The screen will be probably
98 strange noises will be heard from inside the m
99 all consistent video modes supported by your B
100 ``ghost modes``). If you are afraid this could
101 this function.
102
103 After scanning, the mode ordering is a bit dif
104 modes are not listed at all and the modes reve
105 all VESA modes.
106
107 Mode IDs
108 ~~~~~~~~
109
110 Because of the complexity of all the video stu
111 used here are also a bit complex. A video mode
112 expressed in a hexadecimal notation (starting
113 by entering its mode directly if you know it e
114
115 The ID numbers can be divided to those regions
116
117 0x0000 to 0x00ff - menu item references. 0x
118 outside the menu as this can change fr
119 have used the ``scan`` feature).
120
121 0x0100 to 0x017f - standard BIOS modes. The
122 (as presented to INT 10, function 00)
123
124 0x0200 to 0x08ff - VESA BIOS modes. The ID
125 0x0100. All VESA modes should be autod
126
127 0x0900 to 0x09ff - Video7 special modes. Se
128 (Usually 940=80x43, 941=132x25, 942=13
129 945=132x28 for the standard Video7 BIO
130
131 0x0f00 to 0x0fff - special modes (they are
132 by modifying one of the standard modes
133 0x0f00 standard 80x25, don't reset mo
134 0x0f01 standard with 8-point font: 80
135 0x0f02 VGA 80x43 (VGA switched to 350
136 0x0f03 VGA 80x28 (standard VGA scans,
137 0x0f04 leave current video mode
138 0x0f05 VGA 80x30 (480 scans, 16-point
139 0x0f06 VGA 80x34 (480 scans, 14-point
140 0x0f07 VGA 80x60 (480 scans, 8-point
141 0x0f08 Graphics hack (see the VIDEO_G
142
143 0x1000 to 0x7fff - modes specified by resol
144 form where RR is a number of rows and
145 E.g., 0x1950 corresponds to a 80x25 mo
146 This is the only fully portable way to
147 but it relies on the mode being found
148 (remember that mode scanning is not do
149
150 0xff00 to 0xffff - aliases for backward com
151 0xffff equivalent to 0x0f00 (standard
152 0xfffe equivalent to 0x0f01 (EGA 80x4
153
154 If you add 0x8000 to the mode ID, the program
155 vertical display timing according to mode para
156 eliminate some annoying bugs of certain VGA BI
157 cards with S3 chipsets and old Cirrus Logic BI
158 end of the display.
159
160 Options
161 ~~~~~~~
162
163 Build options for arch/x86/boot/* are selected
164 utility and the kernel .config file.
165
166 VIDEO_GFX_HACK - includes special hack for set
167 to be used later by special drivers.
168 Allows to set _any_ BIOS mode including graphi
169 text screen resolution instead of peeking it f
170 unless you think you know what you're doing. T
171 mode number 0x0f08 (see the Mode IDs section a
172
173 Still doesn't work?
174 ~~~~~~~~~~~~~~~~~~~
175
176 When the mode detection doesn't work (e.g., th
177 the machine hangs instead of displaying the me
178 the configuration options listed under "Option
179 your kernel with the video mode set directly v
180
181 In either case, please send me a bug report co
182 happens and how do the configuration switches
183
184 If you start Linux from M$-DOS, you might also
185 video mode setting. In this case, you must spe
186 current settings") to Linux, because if you do
187 mode, Linux will switch to 80x25 automatically
188
189 If you set some extended mode and there's one
190 bottom of the display containing already scrol
191 contains the most common video BIOS bug called
192 end setting". Adding 0x8000 to the mode ID mig
193 this must be done manually -- no autodetection
194
195 History
196 ~~~~~~~
197
198 =============== ==============================
199 1.0 (??-Nov-95) First version supporting all a
200 setup.S + Cirrus Logic 54XX. P
201 and then removed due to instab
202 2.0 (28-Jan-96) Rewritten from scratch. Cirrus
203 everything is configurable, th
204 stable, explicit mode numberin
205 2.1 (30-Jan-96) VESA modes moved to 0x200-0x3f
206 supported. Few bugs fixed. VES
207 modes supplied by SVGA autodet
208 CLGD autodetect works better.
209 active when started. Scanning
210 Code cleaned up.
211 2.2 (01-Feb-96) EGA 80x43 fixed. VESA extended
212 VESA modes work now). Display
213 Special modes renumbered to al
214 flag, 0xffff and 0xfffe became
215 Screen contents retained durin
216 2.3 (15-Mar-96) Changed to work with 1.3.74 ke
217 2.4 (18-Mar-96) Added patches by Hans Lermen f
218 with some boot loaders. Memory
219 these changes. Unfortunately,
220 only with some loaders now.
221 Added a Tseng 132x60 mode.
222 2.5 (19-Mar-96) Fixed a VESA mode scanning bug
223 2.6 (25-Mar-96) Some VESA BIOS errors not repo
224 several cards with broken VESA
225 2.7 (09-Apr-96) - Accepted all VESA modes in r
226 cards use very strange mode
227 - Added Realtek VGA modes (tha
228 - Hardware testing order sligh
229 contents done as first.
230 - Added support for special Vi
231 (thanks to Tom Vander Aa).
232 - Added 480-scanline modes (es
233 original version written by
234 Jeff Chua, rewritten by me).
235 - Screen store/restore fixed.
236 2.8 (14-Apr-96) - Previous release was not com
237 - Better recognition of text m
238 2.9 (12-May-96) - Ignored VESA modes 0x80 - 0x
239 2.10(11-Nov-96) - The whole thing made optiona
240 - Added the CONFIG_VIDEO_400_H
241 - Added the CONFIG_VIDEO_GFX_H
242 - Code cleanup.
243 2.11(03-May-97) - Yet another cleanup, now inc
244 - Direct testing of SVGA adapt
245 offered explicitly on the pr
246 - Removed the doc section desc
247 functions as I try to get ri
248 2.12(25-May-98) Added support for VESA frame b
249 2.13(14-May-99) Minor documentation fixes.
250 =============== ==============================
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