DOS in yellowish tint with GTX 460

Getting old DOS games working. (DOSBox topics belong in DOSBox areas below, not here).

DOS in yellowish tint with GTX 460

Postby hwh » 2011-6-16 @ 13:57

I've got a new GTX 460 and what do you know, DOS graphics (that is, NTVDM) all have this terrible tint to them. There's no white anywhere. But, on the same card, monitor, system, I get the correct colour with DosBOX. Unfortunately I have no other PCIE cards to test with (this computer is new). Monitor is analog (DVI to dsub), but everything else seems to look right.

I also popped into safe mode, hoping this was some driver fluke, but nay, the colours are wrong, driver or not. I have also tried booting into DOS itself and verified that the graphics are wrong in there too. I asked Gigabyte about this, and they...well...they told me to send the card back to them. I sent the card to Gigabyte, they performed their tests on it, and shipped it back to me with no comment. They don't seem to understand my problem - as far as they are concerned the card works. I also tried posting this problem on Gigabyte's service forum and got no responses!

Just so you can tell what the hell I am going on about, here it is:

This is a correctly coloured bitmap:
Image

One with the new computer:
Image

That's Time to Die you're looking at there.

You might be tempted to say "use DosBOX," but I don't want to unless I'm missing sound emulation (id est Sound Blaster) or the game can't handle clock speed. I have my library of favorites which run just fine...except with this new computer they look all wrong. It's ironic, the 8x14 font is present, but the display looks terrible.
Last edited by hwh on 2012-1-30 @ 05:25, edited 1 time in total.
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Re: DOS in yellowish tint with GTX 460

Postby DosFreak » 2011-6-16 @ 14:33

Are there any configuration or switches in the game to switch it between video modes?

If not try changing the machine type in DOSBox to see if you can get the same color issue.
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Re: DOS in yellowish tint with GTX 460

Postby wd » 2011-6-16 @ 14:46

Also switch to fullscreen (ntvdm) before starting the game.
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Re: DOS in yellowish tint with GTX 460

Postby Tetrium » 2011-6-16 @ 19:53

hwh wrote:I've got a new GTX 460 and what do you know, DOS graphics (that is, NTVDM) all have this terrible tint to them. There's no white anywhere.

So not only plastics yellow over time.


sorry lol, had to mention that :P
Good luck ;)
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Re: DOS in yellowish tint with GTX 460

Postby dvwjr » 2011-6-16 @ 21:14

Since you are using the nVidia GTX-460 video adapter with the NTVDM of Windows, that implies the 32-bit version of Windows.

Which version? And which Service Pack?

Win2K
WinXP
Vista
Win7

Go to this VOGONs post and download the CGA_TEST.ZIP file from user thothie that is named in that message. Extract the WHITE.EXE Dos program and execute it in a Full-screen NTVDM console. Is the color a completely WHITE screen or is it that LIME green shown in your second screen capture?

If the result is green, then try to boot you 'new' PC with some version of DOS, somehow and see if running the WHITE.EXE program gives you either a white or green result...


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Re: DOS in yellowish tint with GTX 460

Postby hwh » 2011-6-18 @ 03:57

DosFreak: I tried a number of machine options in DosBox and as far as I can tell they all look correct.
wd: I can't run them in windows, actually. NTVDM forces me to full screen.
dvwjr: White.exe looks positively blue. The same thing happens in DOS.


By the way...I did some testing and it seems that this only happens in 4 or 16 color games - 256 color dos programs don't have the problem. Therefore, it's happening in CGA and EGA but not VGA.
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Re: DOS in yellowish tint with GTX 460

Postby Tetrium » 2011-6-18 @ 04:58

Could it be that some backward compatibility was scrapped or changed lately?
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Re: DOS in yellowish tint with GTX 460

Postby dvwjr » 2011-6-18 @ 05:42

hwh" wrote:By the way...I did some testing and it seems that this only happens in 4 or 16 color games - 256 color dos programs don't have the problem. Therefore, it's happening in CGA and EGA but not VGA.


Any more information about what version of Windows and Service Pack you are using for the NTVDM used to execute your DOS programs? A few more things you can try, perhaps...

You might want to go to this VOGONs post and download the SVGATEST.ZIP file, extract the SVGATEST.EXE file and try the VGA/EGA/CGA video mode test under both the NTVDM and real DOS with your nVidia GTX-460. Usually nVidia has a very good vBIOS with backwards compatibility, but that might have gone by the wayside since the nVidia 7xxx series of PCIe video adapters.


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Re: DOS in yellowish tint with GTX 460

Postby filipetolhuizen » 2011-6-18 @ 17:12

Probably a Windows update has a bogus VGA.drv. Try searching for an older version of it and see if this resolves the issue.
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Re: DOS in yellowish tint with GTX 460

Postby dvwjr » 2011-6-19 @ 02:26

filipetolhuizen wrote:Probably a Windows update has a bogus VGA.drv. Try searching for an older version of it and see if this resolves the issue.


The VGA.DRV is used in the WinNT family for "Windows-On-Windows" in this case for Win31 apps running under the NTVDM/Win31 environment. The VGA.DRV (and dll files) do nothing for pure DOS applications under the NTVDM, only VGA.SYS matter there. If under real DOS the GTX-460 has problems, then the vBIOS is the problem; if under the NTVDM the problem exists, then VGA.SYS matters.


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Re: DOS in yellowish tint with GTX 460

Postby filipetolhuizen » 2011-6-19 @ 14:21

if under the NTVDM the problem exists, then VGA.SYS matters.

DOS graphics (that is, NTVDM) all have this terrible tint to them.

So, this actually seems to be the problem.
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Re: DOS in yellowish tint with GTX 460

Postby hwh » 2011-6-20 @ 01:28

This is XP SP3.

I ran svgatest and it does this
Image
in "modes D and E." Those are both 16 color tests. The other modes (including some with 16 colors) appear correct. I think the low intensity might be white, but the high isn't.

The results are the same in DOS.

Tetrium: I think you hit the jackpot on that one. At least Dosbox can get around it.
Last edited by hwh on 2012-1-30 @ 05:31, edited 1 time in total.
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Re: DOS in yellowish tint with GTX 460

Postby filipetolhuizen » 2011-6-20 @ 04:19

Oops, nevermind, I read it all wrong. If you tested in pure DOS and it did the same, vga.drv is not to blame.
Last edited by filipetolhuizen on 2011-6-20 @ 05:26, edited 1 time in total.
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Re: DOS in yellowish tint with GTX 460

Postby dvwjr » 2011-6-20 @ 04:53

hwh wrote:This is XP SP3.
.
.
.


If you have the time you might use the vBIOS utility NiBiTor v6.02 located here at the mvktech.net website and grab a copy of your vBIOS from the GTX-460 video adapter. Then post your GTX-460 vBIOS here as an attachment and I can take a look at the tables and code. May not help but if the green channel problem with the high intensity values is in error for both the VGA and DVI outputs then perhaps it can be fixed...


Let me know,


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Re: DOS in yellowish tint with GTX 460

Postby hwh » 2011-6-21 @ 03:06

Thanks, here it is. :happy:
Attachments
GTX 460.zip
vBIOS
(43.83 KiB) Downloaded 336 times
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Re: DOS in yellowish tint with GTX 460

Postby dvwjr » 2011-6-23 @ 05:01

hwh,

Thank you for the copy of your GTX-460 vBIOS. It appears that nVidia has changed the vBIOS from the original Weitek source code approach, so more disassembly will be required. If you can run some debugging tools for me on your WinXP (SP3) PC then I may be able to proceed. I know what the problem is, I just have to find the code in the vBIOS ROM to fix the problem.

The nVidia vBIOS ROM used to have a 'hack' for the EGA/VGA 200 lines (default 16 CGA color) video modes 0x0D (320x200x16) and 0x0E (640x200x16) that would just stuff the DAC with the below color values.

Code: Select all
CompatColors    db     0,1,2,3,4,5,14h,7,38h,39h,3Ah,3Bh,3Ch,3Dh,3Eh,3Fh


So in your example of VGA/EGA mode 0x0D the high intensity colors (above values 0x38 to 0x3F) all have a low green component added to each R'G'B'RGB color. The 'hack' might have been removed and if they created the palette values by 'walking' the color triangle with a table of intensity values - the error could have occured if this method was used for the first 16 palette values.

To check for either table or formula palette generation I need some more information that can only be generated from your WinXP (SP3) PC. If you have the time (and interest) then please PM me and I can arrange to get these few tools and instructions on their use to you. I am also curious as to the results of the SVGATEST program on video modes 0x04/0x05 and the 16 color 640x350 video mode 0x10. Do this video modes output colors properly or do they have similar 'tint' errors as do EGA/VGA video modes 0x0D and 0x0E ???

Remember, the video BIOS, while necessary for initial boot, is considered legacy code by nVidia and it partners, so no fix for old VGA video modes will be forthcoming. Even though you sent your nVidia GTX-460 video adapter back to Gigabyte, they have no clue about the vBIOS and older VGA video modes and frankly would wonder why anyone would still be using them...

I had to take apart the nVidia 7950GT vBIOS to make all the VESA video modes work at 85Hz for my LaCie Electron 22 Blue IV CRT monitor on my WinXP (SP2+) system, since the default refresh rate for all VESA video modes had been fixed at 60Hz for LCD and CRT monitors. It looks as if the vBIOS has been re-coded - but hey - it's only code. :happyhappy:



Thanks for your time,

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Re: DOS in yellowish tint with GTX 460

Postby hwh » 2012-1-30 @ 05:34

Well, I had a long conversation with this guy about what I could do to solve the problem, and he said he was going to help me with some tools and just pick out the problem in the vbios like he said. That was in August. Unfortunately he has vanished off the face of the earth, so no one is left to help.

For what it's worth, I know why this is happening now.
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