pouët.net

In order to save 4 bytes compared to the standard VESA mode initialization for high resolution video modes (mode numbers > 100h) i wrote a mode finder (vga, graphics, 256 colors) that abuses the address calculation overflow of the VGA BIOS to write and read a pixel to determine the width of the screen, then after scanning, report every mode with a width greater than 0 (and assuming the width is less than 4000). I took some subroutines from "vesamodes.com" which lists all the modes above 100h. I didn't find something similar for the modes below 100h, so i did it myself. Dosbox reports mode 13h and 69h, my GT1030 and GT105M a lot more (see picture show)

code : here
binary : here
imgur picture show : here

As a by-product, my pet intro Dragon Fade now runs in 1360x768, while still being 32 bytes and having ESC support.

So now, for the questions:
Is there already a tool that does find these modes?
How to find the height of an unknown mode?
Can this be extracted from any VGA registers? (i tried and failed)

wow, that's nice tool, thanks! :) as far as I know, WHATVGA from VGADOC package can find those "hidden" modes too and also allow to fiddle with VGA (and even some extended RAMDAC) registers.
you can also probe mode width via BIOS data area, and also get mode height as well (get a byte from 40:84, add 1 to it and multiply by word at 40:85)


technically it's possible, but keep in mind that SVGAs store high bits (those exceeding VGA limits of 8 bit per horizontal/10 bit per vertical timing position) of timing parameters in extended registers, whose layout is different from one vendor to another (and they are often protected so you can unlock them before reading!), so only VGA parts ([3d4 index 1]*8 + 1 for width and Vertical Display End register, scattered across many other regs for height) of those timings are available without tricks ;)


p.s. those "hidden" (and generally only available via VESA modeset call) are often a result of BIOS optimization to use same routines for mode init as for VGA modes, at least S3 does this, and jugding by your screenshot NVidia also :)

On my 1050 secrets.com finds only 13h, 21h, 22h, and 3Fh.

I wrote my own version of the test routine:

Runs with more results:

@wbc: whatvga is nice! works like a charm under dosbox, with lots of features, but fails to work on freedos (runtime error 200, even with all restrictive parameters from whatvga.doc) i tested the idea with the bios area, but i get very strange results for the height, they seem not to match at all :/

@tomcat, your version gives the sames modes for my GT105M that "secrets.com" gives, plus lot of "4096 width" modes which i clearly do not have :D On the fly, i can't (or won't :) spot the difference, so what are you doing differently?

@tomcat, and more importantly, how does the patched dragon look on your system? =)

@tomcat (i forgot, the @F in your code should be @@ right?)

4096 could be 1024 in 32 bit modes... @F means the next forward local label (@@:) My test works on integrated intel gfx also, but completly different results.

@tomcat, i thought the same, one of the modes of the GT105M which i suspect to be true color because of the "blue-only palette" is reported with width 1360 by both your and my version. Between 0x4B and 0x4D (both 1360 width) there is 0x4C which is reported with 4096 by your version and might in fact be true color, the mode exists and can be set, but the patched dragon is in fact invisible there (setting pixels via bios doesnt work there). Anyway, it should report 5440 then ... seems there is still a bit of work to do right? Somewhere, somehow, the correct width/height/depth of the modes should be listable =)

Just for completeness : the source and the source of the -> source of "vesatest.com"

@HellMood here is the program, what you were searching for

nVidia

Intel

hah it's well known CRT bug, try TP7P5FIX or any other patcher :)

Here is the final version of my test code:
http://www.pouet.net/prod.php?which=81202

So the thing is,
generally you can set up the VESA video modes by short mode numbers.



is the same as



But the previous short code only works on PC with integrated intel gfx,
the second one works with intel, nvidia, dosbox and winxp as well.

@tomcat, great work. so the modes in question for the "blue-only" palette are in my case (GT105M)


From these, 0x4C is available, but setting pixels via BIOS does not work. But really more importantly, in mode 0x4D - in true color! - the BIOS pixel setting seems to address the blue channel! I have never heard of that behaviour, in fact i doubt that this should even be happening. Anyway there is now a VERY short way of doing true color effects in very high resolutions (once you know the mode number) and i really like that.

Now i'd like to establish that for every 256b (freedos) competition, THIS tool is run amongst others (like "whatreg" to show the starting values and "showme" to display the first 256b of the current segment) and the information made publically available before the compo (for example Function 2019)

@wbc, thanks again! that works, but the "vga mode test" shows weird results. if i run the "vesa tests" then it shows me (correctly) all the VESA modes, but without their "secret" number. well, since tomcat's final version display them, i'll just use both tools.

Can you "publish" the xmodes tool to the vorgons forums? i'll think that will be a nice addon to the toolkit =)

Now i tested ALL true color modes for GT105M and GT1030. For the GT105M, ALL modes behaved like "256 shades of blue" modes, meaning, setting a pixel via BIOS puts that pixel into the blue plane. The GT1030 behaves differently though, writing a pixel via BIOS has the same intensity regardless of the value (so it's monochrome basically) and the color varies with the mode used, sometimes it's blue, sometimes it's green. So, no general "shades of blue" behaviour :|

Have you tried to write directly to the video memory? It should work.

I didn't make myself clear enough, i EXPLICITLY want to try the limits of using pixel setting via bios (AH = 0x0C, int 10h), since it's very short. It had been wonderful to get a blueish 256 colors palette for "free" with that trick, but apparently it only works on the GT105M ;)

I tested on Intel HD4000 and Nvidia GTX780, the results are consistent with the ones published here, so I guess one can assume a similar behaviour. Just with my old AMD Sempron Mobile onboard X300 laptop the tool doesn't output any result at all...anybody out there with AMD graphics to test ?

@Kuemmel, perhaps the information retrieval with VESA does not work? The card should be new enough to support VESA though ... What does secrets tell you?

I still have to test stuff on two further old notebooks at home. Will keep you all updated =)

Secrets seems to do something at first and then crashes, black screen of death on that AMD laptop...okay it's more than 15 years old and not quite common...

hacked XMODES a bit :) shaved 5 bytes then added debug features (PC speaker squeaking and displaying current testing mode number on POST card :)

and what it gives for my PIII/DOS machine' GeForce FX5500:


so, apparently NVidia keeps mode numbers constant through GPU families, so using these modes are safe on them.

unfortunately, it seem to output nothing on S3 Trio3D/2X (i assume video BIOS doesn't support VESA mode info extraction for those modes); secrets seems to test for a couple of minutes then hangs :(

FreeDOS on my GTX 1080 with a 1920x1200 monitor gives:

So the overlaps agree, but there are a lot fewer of them (and then the 1920x1200 ones and a few more on top).

New XMODES version is out :-)

Result for AMD Radeon R5 M430
Result for ATI RADEON 9600 PRO

BTW these secret short codes are rather useless.
If I set up a hires mode with this short code, then the bank switching doesn't work.
(unless the video mode was set up by the vesa function before...)

so wait, i'm confused... this is about invalid modes or...?

@Tomcat thanks for putting the effort into it! =) A pity if bankswitching does not work, but as long as setting pixels with "int 0x10, ah=0x0c" works that is some very compact setup for doing (still) hires in extreme tiny intro :)

@Parzival, these modes are legal, it's just a shorter - hardware dependent - way to set them up. Unless you are really desperate for free bytes you should always go for the "standard" (VESA) way of setting hi res graphic modes.