Intel i5-8400 Thermals
Thermal testing is tricky for CPUs, as comparative data really only properly works if done on the same architecture, and ideally on the same motherboard. This can be negated with hardware measurement tools (something we are now building), but software monitoring works best when done within the same generation. Sensors can be moved, renamed, or averaged differently, which means that even same-company thermals (Intel vs. Intel or AMD vs. AMD) may not be a linear comparison. Auto voltage testing also means that the motherboard makers are largely in control of how high the temperatures go, but we can still look at the i7-8700K thermals and the i5-8400 thermals, with some additional perspective provided by the i9 CPU series.
NOTE: Some of the above data cannot really be cross-compared, e.g. between i9 & i7 CPUs, as the motherboard and CPU change so drastically.
Comparatively and just with out-of-box configuration, as we figure that’s what most people will use with an i5-8400, we found the CPU to be thermally sound in comparative testing versus the i7-8700K (using an X62 for comparative data). Keep in mind that workload and power consumption are what dictate thermal performance: HCC CPUs have a significantly larger die, a bigger substrate to sink into, and (we think) use a better version of the Dow Corning TIM. There’s also a difference in motherboard and platform, which means a difference in voltage behavior.
Regardless, the i5-8400 performs well here. Part of the 52C average core number is a result of the lack of hyperthreading. The i7-8700K spins-off two AVX threads per core, which increases per-core power consumption and load. That’s where the extra 23 degrees comes from, on the stock version of the 8700K.
There’s not really any need to delid the 8400. It’s good enough as is, and reducing thermals won’t gain us that much in power leakage reductions. You get about a 4% reduction in power for every 10C drop, and there’s just not much room here for more of that.
Intel i5-8400 Power Consumption
Cinebench Multithreaded Power Consumption
Thermals relate to power consumption directly. For Cinebench multi-threaded workloads, we’re measuring about 54W on the EPS12V cables to the CPU, positioning the i5-8400 at about equivalent power consumption to the overclocked R3 CPUs, and just below the previous i5-7600K CPU. We’re still adding the likes of the R5 1600, 1500X, and 1400 to these charts, as we recently completely redid our CPU testing methodology, but we do have R7s and the 1600X present. The R7 1700 measures at 76W, with the i7-8700K at 91W, providing some context to the 54W consumption.
Cinebench Single-Threaded Power Consumption
Single-threaded Cinebench performance has us at 16W, making for improved performance-per-watt in single-threaded tasks. This is where Intel has traditionally excelled, and that remains the case here.
i5-8400 Blender Power Consumption
For a real-world test, Blender pushes the 8400 to draw 57W under full load, tying it with the overclocked R3 1300X and i3-7350K. For comparison to a previous i5 CPU, the i5-7600K measures at 62W, or about 8.8% higher than the 8400. The current-gen flagship 8700K CPU tests at 96W stock, or 130W overclocked.
3DMark Physics CPU Power Consumption
3DMark’s CPU-constrained physics test gives an idea for synthesized gaming consumption, linking the i5-8400 to ~41W power draw. The i5-7600K draws about 43W, with the i7-7700K at ~49W. The R7 1700 is at around 55W, in this particular test.
Prime95 29.2 8K Power Consumption
The above is a Prime 95 29.2 8K power consumption torture, representing one of the worst possible cases for the CPUs.
Total War: Warhammer Power Draw
One more, here: This chart is sparser, as we were forced to collect new data when Total War updated its benchmark routine. The lower TDP R5s and R3s aren’t yet represented. We’ll get there. For now, the i5-8400 plots at 37W consumption during the Total War gaming scenario, with the R7 1700 at 47W and the i7-8700K at 52W. The spread isn’t huge, here, and shows what you can expect from a CPU-intensive game.