Thermal Performance

For CPU water block thermal performance, I use my Core i7-5960X on the Asus Rampage V Extreme motherboard with the CPU overclocked to 4.4 GHz at 1.3 Vcore, paired with 4x4 GB Corsair Dominator Platinum DDR4 RAM at 2666 MHz (CAS16-16-16-18). A Swiftech MCP35x2 pump, an Aquaero 6 XT controller, and a Black Ice Nemesis GTX 480 radiator with Noiseblocker NB-eLoop B12-3 fans complete the loop. The GPU is not placed in the loop to make the only source of heat the CPU and, thus, the CPU block itself. Average flow rate is set to 1 GPM and calibrated in-line temperature sensors are used to measure the coolant's temperature.

Everything required is placed inside a hotbox, and the ambient temperature is set to 25 °C. Gelid GC-Extreme is used as the thermal paste of choice and cure time is taken into consideration. Three separate mounts/runs are done for statistical accuracy and to remove the chance of any mounting-related anomalies. For each run, a 90 minute Intel XTU stability test is performed. XTU is a stability test from HWBot that uses a custom preset of Prime 95 (no AVR), which ensures the load is uniform on each run. CPU core temperatures are measured using Aida64, and the average core temperature is recorded at the end of each run. A delta T of CPU core and loop temperature is thus calculated for each run, with an average delta T that is then obtained across all three runs. This way, the cooling solution is taken out of the picture. The effect of block orientation is also tested, and the best orientation is used for these runs, with the result shown below.


As it turns out, the Phanteks Glacier C350i is not a bad block at all. Giving credit to their engineering department thus, they did manage to make that unique design work. That said, despite the absolute difference not being a lot, even compared to that special block from Aqua Computer with the per-CPU contact tuning, there remain many blocks that outperform this one. There are even older blocks that do better here by simply adopting a tried-and-tested approach when it comes to coolant flow. Phanteks could have arguably eeked out more performance by going with a higher fin density and adopting the split central-inlet flow with a jetplate, and I still am not convinced about the way they went about it here with that small gap on the outside of the fin stack being accessible to the coolant, but things might have also turned out for the worse if they had gone with more fins over the same surface area.