I've got a Palit GTX 580, the 3GB monster. How high would you guys think you can overclock a 580 in terms of core, shader and memory speeds? Mine is running at 885, 1770 and 2010, after playing with V tune, I think from memory, and it never gets above 78 degrees after 15 minutes of Furmark. Is 900 or even 1000mhz possible or even worth the risk?
It's all about the voltage and temps. Most 580's do not let the voltage exceed 1.15v, and 1.15v is generally regarded as safe as long as your temps are in check, meaning 75c or less. For a 24/7 setup around 1.1v is usually what most people do.
OCing differs from one GPU to another depending on the PCB and cooling.
For how to OC, increase Core clock by 50 MHz, Memory Clock by 100 MHZ, Shader Clock by 60 MHZ, then test stability your OC (play games, use stress GPU test) if you're fine, bump up Core, Memory, Shader Clocks by (xxx MHz) and test your OC results.
Note 1 : Check your GPU temp after each Overclock.
Note 2 : Don't mess up with voltages cause you can kill your GPu instantly, if you're unstable (BSODs,crashes, freezes) bump up voltages a little bit.