As well as in the Core i7-8700K, Intel improved their Core i CPUs in the eighth generation in their main limitation, the lower core count, when compared to the AMD competitors.
The Core i5 CPUs have been, for a long time, some of the best options for the user who wants a computer for work or gaming, focusing on cost/benefit ratio. Now, with the new Core i5 family bringing six physical cores, and not four like the models before, the Core i5-8400 is a lot faster than its predecessor, the Core i5-7400, in professional tasks like video and image processing and improving game performance.
Compared to its direct competitor, the Ryzen 5 1500X, the Core i5-8400 is still faster in games (which the seventh generation model already was) but now the extra cores make a difference and it’s also faster in tasks that use all the available threads.
Our most important conclusion is, actually, a surprise: in all of our gaming benchmarks, the Core i5-8400 performed similarly to the Core i7-7700K and even to the new Core i7-8700K. It makes us conclude that the Core i5-8400 is a better option for gaming computers than the Core i7 models since it offers the same performance, and costs half the price.