NVIDIA GTX 690 Review @ OCC
 

The highest clock speeds I could reach on this card are 1202MHz on the two cores and 1620Mhz on the GDDR5 memory. To reach the highest clock speeds I adjusted the GPU core voltage to a maximum of 1175mv and raised the core clock speed by 100MHz and proceeded to test stability using Unigine Heaven Benchmark 3.0 at a resolution of 5760x1080 using the maximum settings. I continued in 10MHz increments until the benchmark failed. Failure came pretty quickly at just +123MHz for a +13% increase in clock speed or 1028MHz. GPU Boosted clocks ranged from 1189MHz to 1202MHz in this configuration. To get the most from the GDDR5 memory I followed the same scaling and ended up with a memory clock speed of 1620 MHz or 6480MHz effective or an 8% bump in speed. Although not massive increases on a percentage basis the increases deliver measurable increases in performance across the board from an already fast card.

http://www.overclockersclub.com/reviews/nvidia_gtx_690/