Hy guys,
I've recently bought an ASUS 780ti at a sortofabargain price to pair up with my Gigabyte one. So, 780ti SLI, bring in the uberframes and let's get down to some 2k goodness! No, not really...
I had a problematic weekend at the beginning of the month trying to get the second card (an ASUS DirectCU II OC) to actually work. I found out that some people had problems with them and had to underclock them to actually get them stable enough. The factory bios with the factory oc was, well, not good.
The screen went black and the pc rebooted when under load at stock oc speeds and sometimes it dropped out even at underclocked settings. Anyway, after a bit of research and plain old geeking about, I just flashed the bios and VOILA', it worked. No more dropouts and reboots as a single card (and it OC properly, although nothing special). That comforted me in believing that the card hardware was not faulty.
So I put the two cards in, eventually set the same skyn3t bios for the two cards (different brands, different bios, but at least the volts and clocks are the same), and they work fine. But FINE was not what I was expecting...
What's the problem then? Well, I've noticed a drop in FPS in many games after about 25/35 mins of playing. As an example, in Far Cry 4 (max settings at 1080p) I get an average of 95fps and it never drops below 75 in the first 25/35 mins. After that, the FPS count drops, even below 55 and then you really notice it stuttering.
Both cards work at about the same load, temps are well within the comfort zone (72°C for the top one and 65°C for the bottom one, the Asus). NO OVERCLOCK, just the stock speeds from the modded bios. I tried pushing it just a bit, but it wasn't stable.
My pc case is nothing special, but the temps are good nonetheless, nothing out of the ordinary and the CPU it's definitely not a bottleneck.
My theory is that my PSU is barely just enough to power the system under load, it's a Corsair HX750W, one of the 80plus Silver series. It pushes out 65A on the +12V rail, and MAYBE I'm pushing it outside its normal efficiency range, it overheats and progressively pushes out less current.
What's your opinion? Am I way off?
Thanks!