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View Full Version : Nforce 3 Chipsets, 6800(all) & AGP Fast Writes Solution.


angelok
09-30-04, 08:44 PM
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=-
09-30-04, 08:49 PM
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
09-30-04, 09:05 PM
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=-
09-30-04, 09:29 PM
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
09-30-04, 09:36 PM
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
09-30-04, 09:38 PM
How about just turn FW off? FW is nearly completely useless anyway. Why should you lower your clocks for FW?

-=DVS=-
09-30-04, 09:42 PM
Oh you saying there might be hardware flaw couseing stuttering on Nforce 3 939 socket mobos with Geforce 6 cards running above 400 :p 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
09-30-04, 09:44 PM
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
09-30-04, 09:46 PM
Oh you saying there might be hardware flaw couseing stuttering on Nforce 3 939 socket mobos with Geforce 6 cards running above 400 :p 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 :retard:

DJB
09-30-04, 10:35 PM
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
09-30-04, 10:40 PM
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
09-30-04, 10:44 PM
Oh you saying there might be hardware flaw couseing stuttering on Nforce 3 939 socket mobos with Geforce 6 cards running above 400 :p 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

angelok
09-30-04, 11:51 PM
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

OK. It seems i am totaly wrong about the ramdac. :bash:
So it's purely to do with Fastwrites and GPU & DDR3 speeds?

At factory defaults (on my card anyway) 425/1100 for 3D/2D & Low Power 3D with Fastwrites on, games stutter and pause consitantly. With Fastwrites off no problems.

At 400/1100 3D/2d & Low Power 3D Fastwrites on no problems. With Fastwrites off no problems.

I guess it's pointless going on about it, I was just curious about why it was happening on the nforce 3 939 boards. I also have a Asus A8V (Via Chipset) that doesnt suffer from these problems.

Regards

Angelo

GenTarkin
10-01-04, 12:13 AM
I think the problem stems from the A64 architecture being such a unique one... It would be interesting to see if this problem also occurs with the VIA counterparts of A64 chipsets.
either way, I just think its because the platform is so new, and there may be bugz not hammered out completely by Nvidia regarding Fast Writes.
Then again it may be crappy video drivers they are developing that are buggy with Fast Writes also.
It also may be some silly register regarding the AGP tunnel on the Nforce boards that manufactures have disabled/enabled in the BIOS that we dont have access too....causing these pauses or halts.
That would explain why some people dont have it and some do...just a combination of wierd settings between the Card and the AGP tunnel that are causing it I suppose...

Im happy that at least Side Band Addressing is not causing any issues, cuz for some odd reason, without it enabled my Nvidia 3d demos dont work properly...they run at like 5fps for some of them lol....and that mermaid is too hot to be seen only at 5fps =P

In order to fix my problem I had to both, sync the cards clock frequencies(2D/3D)....I ended up doing it with BIOS flash after finding most stable clocks...then had to shut off FastWrites in BIOS and use Rivatuners AGP STRAP driver to disable it on the cards end...