m57sli-s4 and 2x 7800 GT SLI issue

[jajay]

hello to everybody ! my name is Gigi and i have a problem.

first of all i have the following configuration:

CPU: AMD Athlon 64 x2 5400+ @2800mhz (default)
mobo: Gigabyte GA-M57SLI-S4
Ram: 2x 1gb Vitesta ADATA Extreme Edition 800 Mhz (dual channel)
VGA: Leadtek 7800 GT 256mb/256bit ; EVGA 7800 GT 256mb/256bit
Power supply: Rasurbo DLP45.1 - 450Watt with active power factor corrector
HDD:  seagate 80GB sata1.5

the problem is: i have these two graphic cards and each one of it works pretty well. when i try to sli them the VGA in the PCI_0 slot is running PCIE @ x16 and the VGA in the PCI_1 slot is running PCIE @ x8; and here comes the most importand problem: if i play any game for 10 minutes the VGA in PCI_0 slot reaches 110 degress Celsius while the VGA in the PCI_1 has only 51. I dont get any errors, the game runs smoothly (bioshock 2) but i have this issue. doesn't mater wich one of the two VGAs i insert in the PCI_0 it always burn when i play anything. i looked everywhere for any setting in the bios and i cannot change the PCI Express bandwith.
i have the latest mobo bios version, i have the latest drivers, i even flashed the 2 VGA with the bios from their  download support sites. i still have the same problem.

if any1 could give me a hint please, anything would be usefull. i could upload some more information or some pictures with the settings, just ask me.


 thx in advance !

[bytheway_r]

Hi and welcome to the forum.

First of all, your motherboard in SLI works as x8/x8 so both PCI-E slots are running x8 speed.

I don't know much about this card but are you sure this is caused by the PCI-E slot? How are the temps if you only use one card in the main x16 slot? The difference is quite huge in your case but generally it's normal for the "top" card to have higher temperatures than secondary card.

For the record, I don't think you can manually change PCI-E bandwidth settings.

[jajay]

hello there and thx for your reply. if i play with only 1 card the temps are ok 45-50 and i tried boths slots with both cards and the temps are ok. when in in SLI mode, only the top card, the one in the PCI_0 , reaches 100+ degrees

i removed the sli bridge so see how goes without it: and so i have 80-90 degrees on both cards, but i get  minus 10-15  fps in bioshock with high detalis, while with the sli bridge i have like 30-40. but still in SLI mode i have 100+ degrees on top card and 50 to 55 on the second. i also might add i don't get any errors or restarts or whatsoever.

and in gpu-z and in Nvidia systeminfo says:
device0: GeForce 7800GT Bus: PCI Express x16
device1: GeForce 7800GT Bus: PCI Express x8
 
i was thinking maybe the top card is running at x16 and heats up that bad and the other one is running at x8 and doesn't
and i was thinking maybe there is a way to lower the pci_0 bus, but i supose you are right, maybe both cards are running x8.. dunno, i really don't know what to try


also if i insert a single card in PCI_1  and PCI_0 is empty it shows x8 while if i insert a card in pci_0 and Pci_1 is empty it show x16, so i really don't know, in mobo manual says that both pci are x16

please excuse my bad english, i really need to improve it

[Dark Mantis]

Hi

I am not sure quite why your top card is getting so much hotter than the bottom one although it is normal for there to be a temperature difference between the cards as the primary one tends to get starved of cool air by the bottom one.

Have you plenty of good cool air flow through the case past the cards ?

[jajay]

well, even if i change the position of the case (switched to horizontal position) the top card is always getting much hotter, doesn't matter wich card is in the first slot the leadtek one or the evga one, i also have alots of space in the case, also it is opened, i always remove the side pannel just to have more ventilation. i also noticed in gpu-z that the the the top card is receiving 1.2 volts while the bottom has 1.4 volts.

i also put the case in horisontal position  and put on the top of the cards an 8cm cooler and now in games i have like 72 degrees on the top card and 45 on the bottom, but still its a huge difference between the two temps.


any other suggestions? anything would be great, thx in advance

[Dark Mantis]

If the top card is getting less volts than the bottom and they are both set the same then in theory it should actually be cooler than the bottom card.

[jajay]

well a 7800GT needs about 125 W and as i remember in school there was a theory that says

if we have a 7800 GT and need 125w power and has 1.4  volts input then it will draw a speciffic current
and if we have the same 7800gt @ 125w power and has an input of 1.2 volts it will draw a different current, typically higher.
the higher the current the higher the temperature due to joule-lenz effect. so i guess that could be explained. but why does the vga cards have different voltages? oO maybe should i increase the voltage for the other vga card? but how? as much as i read arround forums  you need to tweak the vga firmware to be able to do that.

i still haven't manage to do anything about this, i just stay with that 8cm cooler and play like that, but i don't know how healty it is for the PC.
maybe i should sell one card. and quit the SLI thing

[Dark Mantis]

I know what you are saying about the current etc but as a general rule the more voltage you apply the more the temperature rises. It is one of the biggest problems in computing.

[jajay]

problem solved somehow

i sold one vga card to a friend of mine and quit the sli thing i still don't know why i had that issue, it remains a mystery for me but i want to thank you all for the replies and trying to help me.


cheers and take care

[Dark Mantis]

You are very welcome but I would have liked to have got to the bottom of why it was happening.