The Choice
If you’re investing in one of EK’s DIY kits, deciding what to cool is quite easy: Do you buy a CPU kit, or a CPU and GPU kit? If you’re speccing up your own loop from scratch, however, the decision is more complex, but we reckon you may as well cool the GPU and CPU on your first pass.
You can cool memory as well, and the VRMs on motherboards, but at additional cost and risk—particularly for DDR4, as you have to remove the stock heatsinks to mount the liquid-cooled waterblocks. In most scenarios, liquid cooling memory is more for aesthetics than performance. VRMs, on the other hand, may provide significant benefits for overclocking. For that, you need to buy a motherboard with integrated liquid cooling support, or invest in a “monoblock,” specifically designed for your motherboard, that simultaneously cools the CPU and its surrounding VRMs.
There’s also the choice of how many loops. Splashing out on two custom loops is popular. In theory, running each set of components in isolation can reduce overall temperatures, by reducing the temperature of the coolant. For instance, if your GPUs aren’t under load but your CPU is, the GPU idle temps are probably higher in a single loop, due to the increased temperature of the coolant within the pressurized loop. It also looks stellar.
Next, you need enough radiators. The rule of thumb is 120mm of radiator for every component you cool (excluding memory, VRMs, and such), and an extra 120mm if you intend to overclock.