PDA

View Full Version : 8800GTX SLi (volt mods) overclocking issues


HighT3ch
08-31-2007, 01:16 AM
I have a system comprised from an eVGA 680i mobo an E6850 which runs 3900~4000 for everyday use 2 Cellshock sticks with GKX (2GB) and 2x8800 GTXs in SLi. Everything on my system both CPU and VGAs are chilled watercooled (block by eleven for the cpu and 2xEK full cover waterblocks for the cards. Before installing the second 8800GTX card I had one 8800GTX which after volt modding it I could run it 24/7 @ 730/2200. Sometime later I changed the card (manufacturer) did the same mods and I could run the card 24/7 @ 720/2200. I think such variations are acceptable so nothing was strange so far. The current situation is that I now have an eVGA 8800GTX and an ASUS 8800GTX but overclocking in SLi gives me bananas. Both cards were initially volt modded as in the previous cases but 700 MHz in core clock was not stable. Dropped it to 680MHz and same thing as well as to 650MHz. I removed the mods in both cards and 630MHz or even 600MHz core is not stable although a 620-630 core clock is 'normal' for even air cooled cards not fully chilled water cooled ones. I suspect my PSU but I find it difficult to accept that it cannot hold 2xGTXs in 'near' stock speeds. I have a TT toughpower 750W and when monitoring it through a watt-meter I don't see huge surges in watts. The requested watts are well below the nominal wattage the PSU gives. Can someone explain to me what may be the reason ocing in SLi gives me bananas?

gatti-man
09-01-2007, 06:35 PM
I have an oc'd rig with 2 8800gtx's and a qx6700. While neither of my cards are volt modded yet i experienced instability on a toughpower psu when i installed both. The short answer is that tough power Thermaltake psu's are junk. I sold it and got an 1100w tagan psu. Everything has been fine since. I just run mild overclocks on both now of 630/2000. I want to vmod but i dont soldier to well. My cpu runs 1.45v 3.25ghz/1300fsb 4-4-4-12 1t ram (4gb) at 2.3v 1.3v fsb. Drop dead stable now.

The long answer is that i called thermaltaker and got the run around. They blamed everything from my build to switching connectors and on and on. No one really had an answer besides "its sli certified". After a week of testing and trying different things i just ebayed it. Im never cheaping out on a psu again. Ive gone through 3 on my rig before settling on the tagan.

HighT3ch
09-02-2007, 03:27 AM
Hmm, thanks for telling me this. I'll check again.