a little bit like 20 on core, and 50MHz on shader, more or less . its the temp/noise made me changed it .... stock cooler was hot and loud ... i hate both of those ... try playing crysis demo... u will get higher temp than ATI tool .. at least for me it did.. with stock cooler i was getting 60C with fans @ like 70% ... it was loud @ 70% ....
imo its all about vGPU ... if ur manufactuerer decide to give u more vGPU , and bam u OC higher .... i water cooled my old GTS , and it didnt oc higher even though it was like 45C full load .... vs like 60C stock