Meet Intel's Core i5-8400
There's no doubt that AMD's Ryzen processors challenged Intel's position in the desktop PC market this summer. Seemingly in response (though we all know this stuff is planned way in advance), the Coffee Lake-based Core i7 and i5 CPUs landed with six cores each. That was a first for Intel's mainstream platform.
The Core i5 series typically offers enthusiasts the best performance for their dollar. But with those two extra cores, Intel's highest-end Core i5 is now faster than Core i7-7700K in most games, and even in some applications. This means the Coffee Lake Core i5s basically replace last generation's Core i7s. Talk about a huge step forward. Now the mid-range chips can backstop top-end GPUs without becoming bottlenecks.
For more information on Coffee Lake's impact in the mainstream space, check out our Intel Core i5-8600K Review. Today, though, we're focusing on the less expensive, but multiplier-locked, Core i5-8400.
| Active Cores | Base Frequency | 1 | 2 | 4 | 6 |
| Intel Core i5-8600K | 3.6 GHz | 4.3 GHz | 4.2 GHz | 4.2 GHz | 4.1 GHz |
| Intel Core i5-8400 | 2.8 GHz | 4.0 GHz | 3.9 GHz | 3.9 GHz | 3.8 GHz |
| Intel Core i5-7400 | 3.0 GHz | 3.5 GHz | 3.4 GHz | 3.3 GHz | - |
Like the more expensive Core i5-8600K, Intel's -8400 features six cores without Hyper-Threading. Aside from its locked multiplier, the key differences boil down to clock rates, thermal design power, and price. A 2.8 GHz base frequency is the lowest of all Coffee Lake-based processors, including Intel's Core i3 models. That's because the company had to squeeze into the -8400's 65W TDP, while Core i5-8600K gets a 95W rating, allowing the same silicon to accommodate a 3.6 GHz base.
On the surface, a lower clock rate looks bad for performance. But remember that Intel's Turbo Boost technology accelerates frequencies within certain parameters. This allows the -8400 to go quite a bit faster in workloads that don't tax all of the -8400's cores. As you can see in the table above, the 8400's multi-core Turbo Boost bins get a lot more aggressive than Core i5-7400's. And they only trail the -8600K by 300 MHz.
Core i5-8400 drops into a LGA 1551 interface, but as we know from our previous Coffee Lake reviews, it isn't backward compatible with 200-series motherboards. That means you'll have to step up to a 300-series motherboard, even though that means getting no new features in the process. Worse, a rushed launch means the Z370 chipset is your only option for now. Cheaper B- and H-series motherboards, which will cost a lot less, arrive at the beginning of next year. The Core i5-8400 is a locked processor anyway, so the reason most enthusiasts would have had for spending extra (overclocking) doesn't apply here.
Intel cites a $182 recommended customer price, which is the same as its Kaby Lake-based Core i5-7400. That'd be a great value for 50% more cores. However, poor supply means that the -8400 is popping in and out of stock, selling for as little as $200 when the big shops receive a shipment. When they run out, smaller vendors run the price up closer to $260. That's Ryzen 5 1600X territory. AMD also has an advantage in that you can plug its Ryzen chips into B350-based motherboards selling for as little as $80. At least the competing models both include bundled coolers; we don't always get such a luxury in the high-end space, where you're often expected to supply your own thermal solution.
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