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Final Analysis
Intel's Core i5-8400 is the cheapest modern six-core CPU, if you believe the company's recommended customer price. That's quite the feat, given AMD's competitive Ryzen 5 family. Although the -8400 ships with the Coffee Lake line-up's lowest base clock rate, that frequency is offset by more aggressive Turbo Boost bins. As such, lightly-threaded apps spin up nicely, while parallelized workloads benefit from six physical cores working together.
Given Core i5-8400's pedigree, most of us are probably here to learn more about the chip's gaming alacrity. We plotted its performance using average frame rates and a geometric mean of the 99th percentile frame times (a good indicator of smoothness), which we convert into an FPS measurement.
Newer titles are often optimized to extract more performance from CPUs with more than four cores. Our suite includes six games released in 2016 and five older titles that launched in 2014/2015. So, curious whether the latest Intel and AMD many-core processors contribute affect frame rates in a positive way, we're including a chart that breaks out the newer games on their own.
CPUs below the $200 threshold are our key focus, and in its price class, Intel's Core i5-8400 provides the best gaming performance in spite of its locked multiplier. Even when we include a stock ~$215 Ryzen 5 1600, the Core i5-8400 holds its lead. It's only after shining a spotlight on the newer games using an overclocked 1600 that AMD carves out an advantage. Then again, processors in this price range are typically paired to mid-range graphics cards (rather than GeForce GTX 1080s), so you might not see much difference between the comparable AMD and Intel chips.
More important, Core i5-8400 wrecks the Core i5-7400. It's also faster than a stock Core i5-7600K. It can't quite match a Core i7-7700K, like the -8600K, but you're still getting a ton of value, given the similar price point as Core i5-7400.
Moving on to the application charts, Core i5-8400 distances itself from other processors in its price class, beating the previous-gen -7600K in threaded workloads as well. That's downright compelling progress from one generation to the next. Of course, stepping up ~$30 and overclocking a Ryzen 5 1600 should get you similar performance as a Ryzen 5 1600X. And in that case, you'll definitely outperform the Core i5 in heavily-threaded workloads. The compromise is lower performance in lightly-threaded apps and a higher price tag.
Intel's hasty launch means we're stuck pairing mainstream CPUs to higher-end Z370 motherboards until early next year. That's not a great option when you're dealing with a multiplier-locked CPU. Fortunately, the least-expensive Z370-based platforms sell for a reasonable $120. We're far less enthused about Coffee Lake supply issues causing prices on Core i5-8400 and other models to soar through the roof. Many retailers are selling the -8400 for $200 and higher. Hopefully, Intel can address this issue sooner than later. At least you get a bundled heat sink and fan as a consolation prize.
Overall, the Core i5-8400 offers incredible value to gamers on a budget, providing you can find the chip selling for Intel's recommended customer price. As supply stabilizes, you should be able to get your hands on an affordable hexa-core CPU that frees up funds for a faster graphics card than you would have purchased before. Balance is a beautiful thing to PC builders, and Coffee Lake delivers in spades.
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