DOS ain't dead - Serious bug in newer nVidia cards VESA VBE

RayeR

CZ,
20.12.2018, 02:20

Serious bug in newer nVidia cards VESA VBE (Users)

Hi, I just tested one GTX 670 and found strange flickering in Build based games and Quake too (https://www.youtube.com/watch?v=TV6EAeP8sI8).
This issue is spreaded to wider range of nvidia families at least 6xx to 9xx.
The problem is !nvest!gated (WTF, why is "inv3stigated" marked as bad word I cannot post?) here on VOGONS https://www.vogons.org/viewtopic.php?f=63&t=57420
It was found the bug is in VBE func. 07 for scrolling/page flipping. For Quake there's easy fix to disable page flipping by "vid_nopageflip 1" command entered in console. But for Build engine based games we don't know.
We also need to discover what all families are affected. Until GT2xx within it's OK. We need to test 4xx and 5xx and then latest 1xxx and 2xxx. So please if you have such card share test results.

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DOS gives me freedom to unlimited HW access.

Laaca

Czech republic,
22.12.2018, 21:14

@ RayeR

Serious bug in newer nVidia cards VESA VBE

Post reply

It is a bit problematic for us to test it. Who from us, DOS fans, has such superb graphic cards?
Is possible to create a image of boot CD with automated and simple test utility? Such test could be acceptable even for non-DOSfanatics.

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DOS-u-akbar!

RayeR

CZ,
24.12.2018, 15:49

@ Laaca

Serious bug in newer nVidia cards VESA VBE

Post reply

> It is a bit problematic for us to test it. Who from us, DOS fans, has such
> superb graphic cards?

It's not a highend, Kepler is 6 year old architecture. I just wrote it here because some DOS users may also have access to decent modern HW. Never mind, I got some more info that helped to localize problem. It seems that the VBE bug was introduced in video BIOS major version line 80.x while 70.x is OK. I also got runtime ROM dumps of both versions (where 70.x is confirmed as flicker-free by the user) so I can DASM them and compare. I think I have enough info but it's just time consumnig...

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DOS gives me freedom to unlimited HW access.

RayeR

CZ,
27.12.2018, 17:09

@ RayeR

Serious bug in newer nVidia cards VESA VBE - wokaround TSR!

Post reply

We was able to make a workaround for buggy nVidia BIOS.
After consulting with Falcosoft user he was kind to wrote a small TSR that changes number of video pages returned by VBE func 01h. This enforces the affected games to not use HW page flipping and use copy buffer instead. Works fine with Quake, Blood, Duke 3D :) Of course I will try to make permanent BIOS mod if I find it in DASM...

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DOS gives me freedom to unlimited HW access.

Mercury127 29.04.2020, 13:32 @ Laaca	Serious bug in newer nVidia cards VESA VBE Post reply
	> Who from us, DOS fans, has such superb graphic cards? i have gtx 1070. but by other simular problem (absolutely incompatible with VDD in win 3x/9x, even in base VGA mode) it not installed in my comp at now. and as this card VERY BIG - me was VERY HARD put out it from my comp... cpu cooler is override pcie slot latch...

Laaca

Czech republic,
29.04.2020, 13:58

@ Mercury127

Serious bug in newer nVidia cards VESA VBE

Post reply

> > Who from us, DOS fans, has such superb graphic cards?
>
> i have gtx 1070. but by other simular problem (absolutely incompatible with
> VDD in win 3x/9x, even in base VGA mode) it not installed in my comp at
> now.
> and as this card VERY BIG - me was VERY HARD put out it from my comp... cpu
> cooler is override pcie slot latch...

True, there definitely are some incompatibilities even on the VGA registers level. For example the Prehistorik 2 refuses to run on my RTX 2060 and complains to "This card is not fully VGA compatible"

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DOS-u-akbar!

Oso2k

29.04.2020, 18:17

@ Laaca

Serious bug in newer nVidia cards VESA VBE

Post reply

> > > Who from us, DOS fans, has such superb graphic cards?
> >
> > i have gtx 1070. but by other simular problem (absolutely incompatible
> with
> > VDD in win 3x/9x, even in base VGA mode) it not installed in my comp at
> > now.
> > and as this card VERY BIG - me was VERY HARD put out it from my comp...
> cpu
> > cooler is override pcie slot latch...
>
> True, there definitely are some incompatibilities even on the VGA registers
> level. For example the Prehistorik 2 refuses to run on my RTX 2060 and
> complains to "This card is not fully VGA compatible"

Do they work with DisplayDoctor or other VBE emulators?

Mercury127 29.04.2020, 20:51 @ Oso2k	Serious bug in newer nVidia cards VESA VBE Post reply
	> Do they work with DisplayDoctor or other VBE emulators? if you talk about SciTech Display Doctor, then this thing dont work for me even w/o 1070 - when i try run any exe from sdd, i just get CauseWay extender crash. so i even not try test sdd with 1070...

Laaca

Czech republic,
29.04.2020, 23:05

@ Oso2k

Serious bug in newer nVidia cards VESA VBE

Post reply

> Do they work with DisplayDoctor or other VBE emulators?

:-D :-D :-D

The last DisplayDoctor is from 1998 or from 1999. It can't know the graphic card from 2019.

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DOS-u-akbar!

Mercury127 29.04.2020, 21:00 @ Laaca	Serious bug in newer nVidia cards VESA VBE Post reply
	> True, there definitely are some incompatibilities even on the VGA registers level. maybe... but from my debugging tries i found only that BIOS cant properly execute some VDD calls. it look as if bios programmer make errata, and code run to C000:FFFF instead return from call...

Berlin, Germany,
23.12.2018, 22:50

@ RayeR

Serious bug in newer nVidia cards VESA VBE

Post reply

> The problem is !nvest!gated (WTF, why is "inv3stigated" marked as bad word
> I cannot post?) here on VOGONS
> https://www.vogons.org/viewtopic.php?f=63&t=57420

Because I'm getting a lot of spam mails via this forum and I'm still inv!stigating the issue.
Sorry for any causing trouble to you.

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Forum admin

Laaca

Czech republic,
18.04.2020, 18:05

@ RayeR

Serious bug in newer nVidia cards VESA VBE

Post reply

I bought a new (quite powerful) notebook and succeeded to install the dual boot Win10/FreeDOS.
It has a graphic chip NVidia RTX 2060.
And it is affected too. I haven't test the patch yet.
And I found other issue - all my programs based on my graphic library VenomGFX have garbaged output.
The reason is formaly correct but strange implementation of VESA standard where length of the scan line is not equal to X-resolution.
For example I set the mode 800x600 16-bit and the pixel (0,0) is on address 0. Pixel (1,0) has address 2 (as we are in the 16bpp mode)
But pixel (0,1) is not address 1600 aka (800 * 2) but on address 2048.
It can be obtained from VESA function 4F01h (BytesPerScanline field) so it is not a violation of VESA standard but it is ugly (I would like to write a czech word "prasarna")
I tried to change the behaviour with the VESA function 4F06h but it does not do anything (I don't know why. maybe is impossible to set less than above mentioned 2048 bytes per scanline). Or maybe is this function crippled - I don't know :-(

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DOS-u-akbar!

Laaca

Czech republic,
26.04.2020, 23:01

@ Laaca

Serious bug in newer nVidia cards VESA VBE

Post reply

Hm...
The VESA function 4F06h:
The function 4F06h is not crippled but completely unsupported. It always return the error code in AX.
And 4F07h
The FalcoSoft patch is working well - tested in Duke3D.
By the way, the function 4F07 is not only visualy ugly (because of the flickering) but it is also sluggish slow. Duke3D in 800x600 is almost unplayable and I estimate the framerate around 7-10 FPS. (and yes, the mentioned patch cures also this problem)

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DOS-u-akbar!