Nforce 3 Chipsets, 6800(all) & AGP Fast Writes Solution.

[angelok]

Hi Guys,

First of I know the simple solution to games stutering and pausing for a few seconds is to turn fast writes off via bios or software.

But I wanted to know why the fast writes / stutering and pausing problem was so random? For anyone that has had this problem including myself you would have tried different drivers, bios versions, bios settings, voltages in the end we just turn fast writes off because nothing fixed the problem (for me anyway).

To cut a long story short.......

I have a ASUS 6800 Ultra 425/1100 (stock settings from ASUS)
Now the 6800 Ultra has a 400mhz Ramdac? So from the outset my card at stock speed is overclocked by 25mhz.

AGP Fast Writes communicates with the ramdac in this case 400mhz. AGP fast writes has a problem when the card is running above it's spec and it tries to reset the ramdac back to 400mhz which causes the stutering and pausing, but it's not succesfull because the card is set to 425mhz so the AGP keeps trying to reset it and we keep getting stuttering and pauses during gameplay.

So just for testing I used RivaTuner to set my 2d/3d and low power clock to 400mhz which equals the ramdac in the card. Turned AGP Fast Writes on and have been testing 3Dmark03 which I could not complete with fast writes on, Rome: Total War which I was having huge probs with fast writes on.
With no problems at all.

Is there is anyone that is having this particular problem that would be willing to run a few tests with the games/apps that are causing problems to see if this will work for you?

Hope this helps


Angelo

[-=DVS=-]

What if your card is GT and it runs stock 350 MHZ would that make DAC run at 350 ? or should it couse stuttering becouse dac must run at 400 according to your info ??

Anyway i don't have Nforce 3 , but got VIA based mobo and no problem with Fastwrites on.

[angelok]

Originally Posted by -=DVS=-

What if your card is GT and it runs stock 350 MHZ would that make DAC run at 350 ? or should it couse stuttering becouse dac must run at 400 according to your info ??

Anyway i don't have Nforce 3 , but got VIA based mobo and no problem with Fastwrites on.

Let's say your 6800GT has a ramdac of 350mhz but your card is running at 400mhz and you are getting stuttering etc... What I mean is lower the clock rate to equal your ramdac (all 3 clock rates which is 2d/3d and low power rate).

The VIA chipset doesnt seem to have this problem.

[-=DVS=-]

So you saying GT and Ultra models have different DAC or even lower models ? i though it was same for all models. In that case it should not matter what megahertz your GPU runs at.

And if GPU MHz equal DAC then what ? Radeons at core 500 have DAC of 500 ? makes no sense realy. I was sure that all todays cards got DAC at 400 ?

Moust common DAC is 400mhz only Matrox got higher a bit over 400 think they got 433,, for example Radeon 9000 Pro got 2x 400Mhz DAC , GeForce4 MX460 got 2x 350Mhz DAC , and they dont run anywhere near those clock frequancys .

[angelok]

Originally Posted by -=DVS=-

So you saying GT and Ultra models have different DAC or even lower models ? i though it was same for all models. In that case it should not matter what megahertz your GPU runs at.

And if GPU MHz equal DAC then what ? Radeons at core 500 have DAC of 500 ? makes no sense realy. I was sure that all todays cards got DAC at 400 ?

No it was just an example all geforce 6800 have a 400mhz Ramdac. What I am saying is with the nforce 3 (Socket 939 by the way) chipset and AGP Fastwrites on if your gpu is clocked higher than your ramdac thats when problems occur. This has worked for me and thats why I asked for others to test this as well.

[Raptorman]

How about just turn FW off? FW is nearly completely useless anyway. Why should you lower your clocks for FW?

[-=DVS=-]

Oh you saying there might be hardware flaw couseing stuttering on Nforce 3 939 socket mobos with Geforce 6 cards running above 400 if it is would be a bummer for Nvidia .

Fast Writes do give a little more FPS , someone do a test if its better then more megahertz.

[angelok]

Originally Posted by Raptorman

How about just turn FW off? FW is nearly completely useless anyway. Why should you lower your clocks for FW?

I knew someone was going to ask me that
I agree with you about FW. I just wanted to know why It causes problems on the Nforce 3 chipset.

[angelok]

Originally Posted by -=DVS=-

Oh you saying there might be hardware flaw couseing stuttering on Nforce 3 939 socket mobos with Geforce 6 cards running above 400 if it is would be a bummer for Nvidia .

Fast Writes do give a little more FPS , someone do a test if its better then more megahertz.

Yes thats what I am saying. Sorry if I confused you. My brain thinks one way and my fingers type another way

[DJB]

What it the world makes you think that the ramdac speed is in any way tied into the GPU speed? Raising and lowering your core speed has no affect on the speed of the ramdac.

DJB

[myshkinbob]

ummm, just a moment. It's always possible i'm wrong, BUT...

Despite the ram in the name, your ramdac (or in the 6800's case dual ramdacs) is solely responsible for generating the video signal for your monitor/lcd from the finished framebuffer. Ramdacs run at 400mhz to provide for signals up to 2048x at high refresh rates. Their frequency is to do with video signal bandwidth. Ramdacs don't have anything to do with the agp interface. if you run 1600x1200@75hz afaik the ramdac is running at maybe ~200mhz, and at 1024x768@85hz maybe 150mhz.

[myshkinbob]

Originally Posted by -=DVS=-

Oh you saying there might be hardware flaw couseing stuttering on Nforce 3 939 socket mobos with Geforce 6 cards running above 400 if it is would be a bummer for Nvidia .

Fast Writes do give a little more FPS , someone do a test if its better then more megahertz.

already done

http://www.nvnews.net/vbulletin/showthread.php?t=36203