DOS ain't dead - 4k resolution under DOS :)

RayeR

CZ,
18.01.2024, 20:25

4k resolution under DOS :) (Users)

Hi, I had a chance to play little bit with 4k LCD connected to my GTX 970. Primary goal is to hack/unlock 4k mode @60Hz under WinXP but I was also curious if there's any chance to get it under DOS too. And it is possible.
But it depends on what kind of connection I use. If LCD is attached via HDMI I got max VESA mode 1280x1024/32bpp however via DP 1.2 I got 3840x2160/8 and 16 (not 32)bpp @60Hz, when switched LCD to DP 1.1 I got the same @30Hz. It's known than nvidia BIOS builds VESA mode list dynamically according to EDID of attached monitor. I don't know if EDID is different for DP and HDMI. I run VESA test on it got decent ~180FPS :)

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DOS gives me freedom to unlimited HW access.

Zyzzle

19.01.2024, 01:51

@ RayeR

4k resolution under DOS :)

Post reply

> Hi, I had a chance to play little bit with 4k LCD connected to my GTX 970.
> Primary goal is to hack/unlock 4k mode @60Hz under WinXP but I was also
> curious if there's any chance to get it under DOS too. And it is possible.
> But it depends on what kind of connection I use. If LCD is attached via
> HDMI I got max VESA mode 1280x1024/32bpp however via DP 1.2 I got
> 3840x2160/8 and 16 (not 32)bpp @60Hz, when switched LCD to DP 1.1 I got the
> same @30Hz. It's known than nvidia BIOS builds VESA mode list dynamically
> according to EDID of attached monitor. I don't know if EDID is different
> for DP and HDMI. I run VESA test on it got decent ~180FPS :)
Very impressive. Your report is the very first I've heard of anyone getting a VESA mode of 3840x2160 under DOS. What does that VESA mode report as using your utility? Are there other modes such as 1920x1440 or 2048x1536 generated as well? My guess is you only get 1920x1080 and 3840x2160 as "additional" modes under DP 1.2. By the way, just what is "DP"? Do you mean "display port" video?

I also fail to understand how VESA modes and / or EDID can be built dynamically. That means the card must not have any cooked in VESA modes in its vBIOS? Where in RAM is the VESA table put? May this "dynamic" VESA mode generation be used with other cards, too? (Like my Intel UHD 620 built-in graphics on my laptops)?

If it's possible to generate "dynamic" VESA modes somehow generically, then we've come a long way toward solving the horribly crippled / disabled vBIOSes on "modern" systems.

RayeR

CZ,
20.01.2024, 03:59
(edited by RayeR, 20.01.2024, 04:26)

@ Zyzzle

4k resolution under DOS :)

Post reply

Yes, DP I mean when LCD was connected via Display port interface.
Currently I don't have access to HDD that I run my experiments, if I remember well there was not any modes between 1600x1200 and 3840x2160, so any other modes was not wide bur classic 4:3. I will post full log later.

I guess that it works this way: after power on the GPU BIOS/firmware checks through available video outputs if some monitor is attached and read EDID from it. It will then know, what is the native resolution. It has some fixed VESA mode table. BIOS is copied from flashROM to RAM so it can change the VESA mode table in RAM and use some free slot at the end to include the native LCD resolution (it's values are probably calculated dynamically). But I don't know why it behaves differently on DP and HDMI. In the past I has similar issues with GeForce 7600 a 7900 where it offered my LCD native 1600x1200 mode only when attached via analog VGA but not via DVI-D - then it show only 1280x1024. I had to hack VESA mode table that I found in BIOS image so then got 1600x1200 on DVI too. On later nvidia GPU 6xx and 9xx it's fixed and I have 1600x1200 with stock BIOS...

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DOS gives me freedom to unlimited HW access.