For a "conservative" OC tool, the NVIDIA App gave me remarkable results ...
Nvidia’s 595.71 driver broke user overclocking, but a fix is here that seemingly patches up the problem.
Nvidia Geforce GTX 275 is a very interesting graphics card positioned somewhere between GTX 260 and GTX 285. It packs all 240 shader processors just like the GTX 285 but it comes with 896MB of memory ...