Of course the ROM is meant there. "Overclocking" means normally to override CPU settings so that the CPU is running at a higher frequency.
for the U960 this means: It is made with a 1Ghz CPU. You can overclock it to 1.2Ghz or even 1.4Ghz. CPUs are mass products with tolerances. 1Ghz is guaranteed by the producer. This means that many CPUs will even work at a higher speed. But take care: Your phone can become unstable due to the CPU is not accepting the speed or will become too hot.
Raising the CPU speeds is mostly not working without also letting the RAM frequency running faster. So also this can result in unstable systems.
At the end everybody should know that overclocking can seriously damage your phone as you are using it out of producers specifications.
To overclock the U960 you only need to update the Kernel so you can overclock without losing all your data.
With baseband 2B03 I overclocked to 1.4Ghz without problems.
with baseband 2B06 and 2B07 my phone became unstable at 1.4Ghz so I use actually a Kernel at 1Ghz.
Hope I could help you. Again: This is a simple explanation and is not meant to be technically 100% perfect.
Thanks for these clarifications, did you experience any change in battery life when overclocking to 1,4 Ghz?
another point is unclear to me: specs show 850/2100 Ghz for 3G, when similar phones use 900/2100 Ghz, is it upgradable by baseband change or is it an h/w feature?
thanks