German overclocker der8auer and his team managed to push the Intel Core i7 7700K processor to 7328.3MHz, with all four cores activated and Hyper-Threading turned on! While most extreme overclocks are done with liquid nitrogen, der8auer was able to use liquid helium thanks to a little help from sponsor ASUS.
The benefit of liquid helium is that it gets you a lot closer to absolute zero, liquid helium is about -269°C which is about 70°C lower than the more commonly used LN2. The reason why liquid helium (LH) isn't commonly used by overclockers is because it's extremely expensive. One liter of LH costs around 40EUR, over 100 times as much as LN2. Furthermore, LH evaporates more quickly so you also need more liters to keep the CPU chilled. One liter of LH lasts only 10 seconds so you need a lot of it to achieve an overclocking record.
In total, der8auer consumed around 100 liters of LH over a timespan of 15 minutes. So a quick calculation learns us this world required cost 4,000EUR in LH alone! Full details at Hexus.