Originally Posted by s74r1
So I've had the chance to test two 690's last month. With boost disabled and voltage forced to 1.175v, the first one did 1163MHz Core & 6445MHz effective memory, and the second one did 1124MHz Core and 7200MHz effective memory (fully stable). After an exhaustive suite of benchmarks, I found the one with higher mem to come out on top most of the time.
With boost and normal voltage enabled, the two GPU's even out at 1.150v/1.165v respectively after heating up past 80c so this one is only stable at about 1100MHz core with those voltages (boosts to 1110 at first, then backs down to 1097 with +52 on core and +596 on mem). I believe nvidia made GPU1 boost to slightly lower volts because it's always hotter due to airflow restriction. This card also seems to make more noticeable electrical noise too.
Pretty bad overclockers though, right? Never had good luck with overclocking EVGA cards...
Intersesting because I've found the same scenario where GPU1 does worse @ 1176 MHz Core & GPU2 1202 MHz Core.
However my Memory over clock is very poor. Most I was able to bench was 3200 MHz Memory effectively.
I've not had any luck with over clocking my last four GPU's I've had in my hands either. GTX 580, 680, 680SC, & 690 all approximately a 14% over clocks on Core and poor 4-7% on Memory.
I've found for my single 120 Hz monitor the GTX 690 is more than enough even at stock. I've settled for a stable over clock of 1170 MHz Core 3121 MHz Memory for a 24/7 over clock for both GPU's unsynched with GPU2 running lower over clocks to match GPU1 1170 MHz.
I did want to try a dual GPU for the first time and confirmed for myself it's got it's pros and cons. I may try two singles next time in SLI instead.