2X 7800 GTX SLi Problems! Please Help!

wrighty83uk · 19 Apr 2007 at 10:22

Hi all

I have had my computer for about 18months, originally i had only 1 XFX 7800 GTX card at the time beacuse it cost me £350 from overclockers and i couldnt afford two. I have since brought another 7800 GTX but a Gigabyte one and attempted to set them up to run together using my Gigabyte GA K8N Pro SLi motherboard (I managed to pick the card up MUCH cheaper this time!).

I know very little about computers and the like so please forgive my ignorance, i hope this is something simple that i have missed!

I opened the computer up, flipped the "sim card" over on the motherboard to read SLi ready and added the second card, then the bridge and finally the metal brace which keeps the bridge in place (i also put power to each of the cards from my power supply). I powered the machine up and it seemed to work fine, i ran 3Dmark05 however and scored less than i used to with only one card... Also i have recently upgraded to Vista 64bit and my windows experience index dropped slightly on the graphics front...

I have uninstalled and re installed what i believe to be the correct Nvidia Drivers and have selected the SLi option in the control panel but still no joy.

I only have one game installed on my PC at the moment which is S.T.A.L.K.E.R and although it ran fine with only one card now all i can see on the screen when i go into the game is the sky with nothing else on the screen.

Any advice would be much appreciated, is this something i could do my self or should i just admit defeat and take it to a shop?

thanks in advance!

pastymuncher · 19 Apr 2007 at 10:39

Is'nt there a problem with Sli on Vista? Is there an option in your bios (hit del on start up) to enable sli? Have you enavbled sli in the drivers control panel and rebooted?

wrighty83uk · 19 Apr 2007 at 10:50

Hi, thanks for your reply!

Im not sure about problems with Vista and SLi, i assumed i would be ok as i have read of people running SLi with no problems. I have been through setup and i cannot see an option that looks as though it would relate to SLi, i have also read the manual for my motherboard and can find nothing in there, although as i say i am not 100% with this kind of thing, could you give me an idea of what options i would be looking for?

After i have installed the "Nforce 4" and "Geforce 7 series" drivers and selected what i believe to be the correct options for SLi the computer does say it needs to be restarted but it still doesnt work when it has been!

Could it be a possible power problem do you think? I have an Antec 480w power supply which does have two PCI-E connectors? Also through the BIOS i have selected each of the cards in turn to display on my monitor and both have output, it just seems they wont work together!

pastymuncher · 19 Apr 2007 at 11:01

480w is probably a little borderline but it is a good brand. If the cards were'nt getting enough power then you would get a message pop up saying that performance had been throttled down. That's what happened to me when i forgot to plug in a pci-e poer plug once.

As for the bios i am not sure what you should be looking for. Some motherboards had an option in the bios that you had to enable to get Sli to work. I never had one that needed me to do this. I thought yours may have been one of the ones that neede this to be done.

Are you using the correct output to your monitor? You need to use the one from the primary (top) card and it should be the inside (left when looking at the rear of the case) output.

Which drivers are you using? I could'nt use 93.71 with my sli'd 7800gt's as i got the exact same problems as you. I had to use 91.47 and had no problems. Try uninstalling the drivers again via add/remove in the control panel. Reboot and reload the drivers. When you have reloaded them reboot again. You should get a message asking if you want to enable Sli. Do it and reboot again. You should then get a message telling you it has been enabled. It should then work.

Try that and see how you get on.

YorkshirePadd26 · 19 Apr 2007 at 11:02

doesn't SLI only work if you have the same brand of card with the same bios installed on each?

I'm not 100% sure on this but I'm sure i've read this somewhere.

You may have to install the same bios on each card.

Not really an sli expert,

pastymuncher · 19 Apr 2007 at 11:06

Not any more. Just the same gpu and preferably the same memory. If the clock speeds are different they run at the speed of the slowest card. Does'nt matter about manufacturer and bios anymore.

wrighty83uk · 19 Apr 2007 at 11:33

Hi

Thanks for the advice i will give it a go later today, now that you mention it althought the cards look identical (Except fot the XFX one having a a metal border) their is a BIOS sticker on each of them in exactly the same place. As i am at work i cannot recall the exact numbers but i do know that one ends in .10 (the Gigabyte) and the other (XFX) .11

will they ever be able to work together or have i gone a brought the wrong card? All the other stickers and numbers match up!

pastymuncher · 19 Apr 2007 at 11:39

Like i said above ^^ it does'nt matter about the bios anymore. That all changed from the release 80 series drivers.

From Nvidias website:-

Can I mix and match graphics cards?
In order to provide optimal symmetric scaling, SLI technology requires the NVIDIA GPUs to match. For example, a GeForce 7800 GTX must be paired with another GeForce 7800 GTX. Likewise, a GeForce 6600 GT must be paired with another GeForce 6600 GT. However, using the latest Release 80 or later graphics drivers, NVIDIA GPUs sold by different manufacturers can be used together in an SLI configuration. For example, a GeForce 7800 GT from vendor ABC can be matched with a GeForce 7800 GT from vendor XYZ.

Will_3rd · 19 Apr 2007 at 11:51

Don't think SLI is doable in Vista end off, it isn't supported yet

gt_junkie · 19 Apr 2007 at 11:54

I gave up with vista and my GX2. Having the performance of a single overclocked 7900gt was not that much fun! :rolleyes:

XP all the way for me for the next 6 months or so i think!

Unless i go R600 of course!

gt

pastymuncher · 19 Apr 2007 at 12:06

I did ask in my first post if there was a problem with sli and Vista. I thought i had read about it somewhere but as i don't have and don't intend to get Vista i did'nt pay much attention to it.

wrighty83uk · 19 Apr 2007 at 12:24

So should i go back to XP? Do you think it will be long before it will work?

Will_3rd · 19 Apr 2007 at 12:25

wrighty83uk said:
So should i go back to XP? Do you think it will be long before it will work?

Yep, might be an idea considering most problems won't be sorted till the first or second service pack

pastymuncher · 19 Apr 2007 at 14:10

Will, just noticed you have the same mobo as the OP. Is there an option in the bios for enabling sli? It's probably the Vista incompatiability thing causing this though.

gt_junkie · 19 Apr 2007 at 14:16

If you can change to XP then do.

Nvidia seem to be doing very little to sort this so i'd just cut your losses. Your game performance should leap quite healthily... i know mine did!

Keep us posted on how you get on though!

gt

Will_3rd · 19 Apr 2007 at 14:32

pastymuncher said:
Will, just noticed you have the same mobo as the OP. Is there an option in the bios for enabling sli? It's probably the Vista incompatiability thing causing this though.

Just checked quickly an there isn't anything SLI related in the BIOS, and the OP has switched over the SLI thingy on the M/B to switch it to SLI ready, so as you say it could be Vista related

wrighty83uk · 19 Apr 2007 at 15:11

Hi all

thanks for your help, i am going to give it a go later and put Xp back on i really hope i can get it working! once upon a time the computer was awesome but now it just seems to do my head in! I will post again tomorrow to let you know how it goes!

one last thing, Will, i have tried to PM you but for some reason i am not allowed. i have had a go at overclocking my computer recently (before trying to add my second card) and have had issues with the motherboard not allowing me to go over 214mhz! I know there is a part of the forum dedicated to this but i have never found anyone else with the same motherboard as me who actually knows how to overclock with it so any advice would be greatly appreciated! i have since reverted all settings to standard while trying to add this card.

Will_3rd · 19 Apr 2007 at 15:18

wrighty83uk said:
one last thing, Will, i have tried to PM you but for some reason i am not allowed.

Disabled on these forums

wrighty83uk said:
have had issues with the motherboard not allowing me to go over 214mhz! I know there is a part of the forum dedicated to this but i have never found anyone else with the same motherboard as me who actually knows how to overclock with it so any advice would be greatly appreciated!

What RAM do you have?, BIOS update might be useful as well

But general jist is keep an eye on the HTT so it stays around 1000mhz, so switch it to x3/x4 in the BIOS.

run the RAM on a divider so it stays as close or below DDR400

CPU voltage just leave it until it doesn't post, everything that says AUTO turn it to normal or a set value, like the PCI-E bus lock it at 100mhz etc

wrighty83uk · 19 Apr 2007 at 15:43

hi

again thanks for your reply, i have 4x 1gig sticks of crucial pc3200 memory. When i have tried to OC it in the past i have just turned up the cpu freq to 214 which is the most it will take. at this it is about 2.35mhz (which i know is not that good) and i notice also by using is it CPUZ that the HT went to about 833 (i think)

I have tried to update the BIOS but not exactly sure what i am doing, i get an error message when i have tried to run the download.

I have no idea how to run the memory on a divider, i find the BIOS options rather limiting! I have managed to turn the PCI express upto 115 though and have the bios option set on turbo although again i have no idea what this does...

As i say i am a bit of a lost cause with all this as it is very new to me, i will try to provide more info later when i am sat at my home PC!

pastymuncher · 19 Apr 2007 at 19:54

You want the pci-e bus locked at 100. If you go over that it can cause problems.

To update the bios use Gigabytes own updater. On my DS3P it's the @BIOS utility. I don't know if it's the same for your board. It does it all automatically in windows and works fine. Well it does in XP anyway.

I still say it's a Vista problem though.