Now it all comes back to me with the extra information supplied......
"With a lower Vcore the system will hang within 2-3 minutes in flightsimulator.".....I'm not surprised as soon as I read ...
"Thermaltake Kandalf case with factory built in liquid cooling system" These systems are now 6-7yrs old and never designed to run the type of loads you're loading onto it ..... I know as i ripped one apart to build my present system........if you're trying to cool the GPU as well
Let me explain a bit more ..... regardless if you're running half inch fitting or 2" fittings for that matter ..... the system is only as good as the smallest fitting or bore size ...... the radiator feed and exhaust tubes on the Kandalf have a 6mm bore .... their for a very, very limited flow rate
In idle and light load things are fine......when you load the system up....not enough flow-rate is available to cool the CPU sufficiently.
You can check this by a temp reading of the inlet temp of the radiator .... I suspect it will climb , and climb under load, .....probably at around 40C (Rad inlet temp) your system will crash at those clock loads ..... the flow rate for a 6mm hole (Flow rate for a set/given head pressure) is 8 times lower then a 12mm (1/2") hole ..... this is a set ratio ....
"Every time you double the nominal bore size, flow rate will increase by a factor of 8 if the pump pressure is constant".....FACT!
If you want those clocks......look at modding and fitting a high performance RAD .... I did
Aussie Allan