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-   -   DVI output & max 60Hz refreshrate (http://www.hardwarecanucks.com/forum/video-cards/23946-dvi-output-max-60hz-refreshrate.html)

trodas October 3, 2009 04:29 PM

DVI output & max 60Hz refreshrate
On DVI was possible only 60Hz. At least my old beta ones, 45.28, can't seems to show more that 60Hz on LCD monitor pluged into the old 5600XT cardie using DVI connection - while the same drivers did not have a problem with 100Hz refresh on CRT.

After some Windows install tweakings, I decided to "give it a try" and check out 53.03 WHQ drivers for the weird "60Hz only" problem. Much to my dismay, the "60Hz only" problem seems to persist.


Dunno why. Even in lower resolution the driver "force" 60Hz. Is there ANY way to lift this limit? Im affraid that if I use ReForce and force the refresh higher, then upon reboot I got BSOD "inacessible device":)

Not that there is anything wrong with BSOD, yet I would rather see another result :)

Forceware (I still like the old Detonators better...) 81.95 WHQ - still 60Hz only:


I beginning to feel that the problem is "somewhere else". I checked the bios setting and yes, there it is - the DDC scanning was skiped on the boot, so it might do somehing bad. Changed it, but no difference... Maybe reinstall again?

Is there any way to check if the GFX card bios properly reporting the capability of more Hz or not? The problem was not when I used the same card with VGA output and CRT monitor, yet using DVI and LCD monitor I running into a 60Hz wall ... :(

Looks like Linux users find a way:

"AllowNon60HzDFPModes": some lower quality TMDS encoders are only rated to drive DFPs at 60Hz; the driver will determine when only 60Hz DFP modes are allowed. This argument disables this stage of the mode validation pipeline.
Now let's hope I can find a way to fix this problem in Windows too...

I reasonably believe that since the 5600XT can do 2048x1538 pixels in 80Hz refresh, then it sure can do 1280x1024 in 75Hz. eVGA says 5600XT it can do 150Hz in 1280x1024:

As the Linux solution suggest, the drivers cap the refreshrate to 60Hz, because they detect "some lower quality TMDS encoders are only rated to drive DFPs at 60Hz"... But since the very same TMDS encoder can give me output resolution of 2048x1538 pixels in 60Hz refresh, then sure as hell it can give me 1280x1024 in 75Hz. As on Linux :)

Now the question is only how to duplicate the Linux nVidia drivers option "AllowNon60HzDFPModes". Anyone can shred some light at this?

I, personally, see only two ways.
1) change/patch/modify the drivers somehow to allow the non 60Hz DFP modes even on 5600XT card
2) change/patch/modify the GFX card bios to not report lower quality TMDS encoder, thus allowing drivers to set up higher refreshrates

Who can help me to get same results on Windows as on Linux are possible?

trodas October 6, 2009 05:31 AM

The BIG question.
How to simulate the Linux option "AllowNon60HzDFPModes", witch I trying to find out unsucesfully. Looks like the TMDS encoder on my poor FX5600XT card fall into some category that says "60Hz only" in all Forceware drivers I tested (45.28, 53.03 WHQ, 81.95 WHQ)...
I see two ways to get more that 60Hz. Okay, there.
1) modify the drivers somehow to disable the check, as the Linux option does
2) modify the BIOS in my FX5600XT to report more modern TMDS encoder, witch is allowed to use higher refreshrates over DVI
3) buy new GFX card - friend 7300GS with the very same monitor and some 75.xx Forceware drivers do 72 or 75Hz refresh w/o a glitch

Yet since these card are not AGP and the FX5600XT got passive (nice quiet Zalman) cooling, the option no. 3 is not very viable one...

Okay, in fact, there is also option no. 4: use Linux, where things (probably) work!

Oh, well.

The Linux drivers only have the very fortunate possibility of override the default settings by the "AllowNon60HzDFPModes" option that let the driver bypass the checks and allow any refreshrate to be set, and hence drive the TMDS to or even over it's limits.
(I heard that it produce funny digital noise effects, if you go over it's capabilities, hehe)

So basically it looks like that I have to search where the "60Hz refresh only on this chip" option of nVidia drivers is stored and then modify it (on installed drivers) and/or then go and modify the drivers to save the option as I want it - eg. leaving up to the user, how hard he want to drive his TMDS :bleh:

trodas October 8, 2009 07:33 AM

My BenQ FP75G LCD panel do support 75Hz refreshrate, it have 5mS response time.
BenQ FP75G 17" LCD Monitor ( FP75G ) - 17" LCD Monitor - BenQ Monitor

On Linux is possible to override the artificial nVidia limit by using "AllowNon60HzDFPModes" paramater. I want the same for Windows.

CanadaRox October 8, 2009 08:10 AM

Unfortunately I did a big "tl;dr" over most of that. But what I gather is you are trying to force 75Hz @ 1280*1024. If the drivers don't want to do it (which seems to be the case), the only other thing I can suggest is using PowerStrip. Its a great little app that can force settings on the GPU such as resolution, refresh rate, gamma, etc. I've used it for a while to force a 1.5 gamma in older games such as Team Fortress Classic. It can force them only when a certain application is run, or on boot. Supports hot keys as well. The only down-side (besides having an extra program running) is that the tips window comes up every boot unless you buy the pro version.

bojangles October 8, 2009 08:11 AM

I wouldn't worry about it. The refresh rate on a LCD is entirely different compared to a CRT. 60Hz is perfectly fine and is the standard of more modern monitors too.

trodas October 10, 2009 06:24 AM

CanadaRox -

If the drivers don't want to do it (which seems to be the case), the only other thing I can suggest is using PowerStrip.
Yes, power strip is great, but prove to be helpless against this 60Hz wall nVidia artificially build for the DVI connections on older cards:


Always ghosted, no help, sadly :(
There IS a way - use ReForce 1.10 to enforce 75Hz to all or all wanted resolutions. The result on the reboot is BSOD as "inacessible device", or so nVidia claims. So, the wall had to be removed first...

bojangles -

I wouldn't worry about it. The refresh rate on a LCD is entirely different compared to a CRT. 60Hz is perfectly fine and is the standard of more modern monitors too.
It is not about worrying about it. It is about scrolling and games that SUXX in 60Hz, compared to 75Hz. Yes, it did not flick. But it update the screen slow, so, that is bad and that is why I want 75Hz. The problem is, that nVidia old TMDS encoders (5600XT have a internal one) used for the DVI outputs are not only integrated, but also inferior. For these reasond nVidia locked the refresh to 60Hz for DVI. Seems as "smart" solution at the time, but proven to be another case of "640k should be enough for everybody".

Check out the 6800 cards, where whole NV40 architecture did not even have internal TMDS encoders and cards had to have external ones:
AnandTech: ATI Radeon X800 XT Mac Edition: Competition in the Mac Market

Or this nVidia log:
Model: GeForce 6800 Ultra

(II) NVIDIA(0): Using ConnectedMonitor string "DFP-0"
(II) NVIDIA(0): Enabled display device(s): DFP-0
(II) NVIDIA(0): Mapping display device 0 (DFP-0) to CRTC 0
(--) NVIDIA(0): DFP-0: maximum pixel clock: 165 MHz
(--) NVIDIA(0): DFP-0: External Dual Link TMDS

There has to be a way to detect the TMDS, drivers must do it, somehow.

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