So i just purchased a 9400f, b365m motherboard, and 16gb of ddr4. My max score on cinebench so far is around 750 with all cores boosting to 3.4ghz. The advertised single core speed is 4.1 but none of my cores are doing that, according to hardware monitor. I fiddled around in the bios as much as I could, eventually resetting it to default settings. This is a fresh copy of windows btw. Any help would be much appreciated.
About why did you bought a 9400F in late 2020, its well beyong my understanding.
Anyways, single core frecuency is up to 4.1GHz indeed, but if you run cinebecnh multi-core test, none of your cores will reach that frecuency.
If you wana test again make it so that Cinebench runs on only 1 core. Look at the menus theres an option to set how many core to run, in fact depending on the version it may have the option on the main screen.
All core frecuency while runing cinebench should go to at least 3.8GHz (it may peak 3.9GHz). As logn as temp and voltage allows it.
Are you using the Balanced Power Plan or Performance Power Plan in Windows?
Are you sure turbo boost is enable in BIOS?
Also if you need further help please put the complete list of your PC parts, include brand and model of everything.