Intel i5-8400 CPU Review: 2666MHz & 3200MHz Gaming Benchmarks

By Published October 15, 2017 at 9:37 pm

Frequency Tests

Before getting further, a quick note on memory frequencies: Intel decided to ship only its Z-series 300 chipsets for now, which means that the more sensible H- and B- series motherboards are not yet available. We’ve heard two stories of the i5-8400’s support for memory speeds: On one side, we’ve heard that 2666MHz could be a maximum supported memory speed; on the other, from board vendors, we’ve heard that there is a possibility of unlocked memory multipliers on some B/H motherboards (permitting up to 32x or 36x speeds). We can’t confirm either right now, so we’re just going to test our standardized 3200MHz – useful for providing valuable, variable-free comparative data – and on a lower 2666MHz speed. The latter will provide useful data in the event that B/H motherboards are limited on memory speed, in which case the lower speeds will better represent real user scenarios.

Before starting the new tests, we’ve got one legacy test for comparative data versus previous Intel generations. Note that testing methodology has changed so significantly across our entire test suite that data is not comparable from our legacy tests, but we are still running a few legacy tests in parallel during the switch-over period. This helps to provide comparative data against the last year of information.

LEGACY: Watch Dogs 2 CPU Benchmark – i5-8400

i5 8400 legacy wd2

This is a legacy test of ours, which means it is deprecated and contains old data. The i5-8400 data isn’t perfectly comparable, as it has a new OS and new GPU drivers, but will give a baseline as to what to expect versus some other popular components. The primary goal is to illustrate scaling versus older Intel CPUs, as we don’t have these units present on the newer charts.

At 1080p/High, the i5-8400 renders about 93FPS in Watch Dogs 2, with lows reasonably high, using 3200MHz memory. This is superior to the i5-7600K when overclocked to 4.7GHz, partly a mix of the core scalability in Watch Dogs 2. Compared to other CPUs of note, the i5-7500 CPU of similar initial pricing performs at 80FPS AVG, marking the 8400 as a 16% increase in performance.

New Tests: Haven’t Fully Added Everything

As we are running these tests in parallel with some older benchmarks, we are still adding CPUs to the charts. This includes, for instance, some of the older Intel i5 parts, AMD R5 parts (we have the 1600X represented, for now), and other previous-gen CPUs. For that reference data, see the above legacy benchmark as a baseline.

Civilization VI Turn Time CPU Benchmark – i5-8400

i5 8400 civ vi time

Civilization VI is part of our newer benchmark suite, and uses turn time completion metrics rather than FPS metrics. The results are similar at 1080p and 1440p.

Time to complete the average turn is about 17.4 seconds with the i5-8400 and 3200MHz memory, or about 17.5 seconds with 2666MHz memory – not a big difference. For comparison, the i5-7600K stock CPU completed the turns in about 16.52 seconds. Overclocking further emphasizes frequency importance in Civilization, where turn time improves by 5.5% with the 4.7GHz overclock. This makes the i5-8400 a step-down in performance from the K-SKU i5, in this particular workload, as Civ VI does seem to favor frequency.

The R5 1600X also reflects this, where we see about a 1.2-second drop from the stock and overclocked R5 1600X values, going from 19.2s to 17.9s. Just for an idea of what a flagship does, the i7-8700K stock CPU completes its turns in 16s stock, or about 15.44 seconds when overclocked to 5GHz.

Keep in mind that turns will lengthen as time goes on in a game, and that you’d multiply this turn time requirement by the number of players in order to determine time before your next play.

Total War: Warhammer CPU Benchmarks – i5-8400

i5 8400 tww 1080p

Total War: Warhammer is first at 1080p. The i5-8400 6C CPU operates at 155FPS AVG, 86FPS 1% lows, and 77FPS 0.1% lows when using 3200MHz CL16 memory. Stepping down to 2666MHz and CL16, the i5-8400 loses 3.8% of its performance and falls to 149FPS AVG, where the i5-7600K performs when overclocked to 4.7GHz. This is also relatively near the 4.1GHz R5 1600X CPU with 3200MHz memory. Performance boosts over the i5-7600K stock CPU by 8.3%, when tested using the same memory speeds. The 8700K is about 14% faster than the i5-8400 at 3200MHz, making for a large price jump that isn’t particularly worth it in this game. Note, however, that we are running into limits with our 1080 Ti. We’ll need other games for a better idea of performance.

i5 8400 tww 1440p

At 1440p, the i5-8400 operates a 138FPS AVG, with lows at 85FPS and 76FPS. We become GPU-constrained at the top-end, similar to what we saw in our 8700K OC limitations a moment ago. 2666MHz performance has us at 132FPS AVG, for a performance decay of 4.4%. At the same memory speeds, the i5-7600K stock CPU operates at 128FPS AVG, or about 6.9% slower than the i5-8400. 1% low and 0.1% low performance scales somewhat linearly. Overclocking the 7600K closes that gap to 4.2%.

The $240 R5 1600X CPU places at 128FPS AVG, with lows at 79 and 70.3FPS. There is no tangible difference in frametime latency or fluidity. Overclocking the R5 1600X to 4.1GHz puts it at 131FPS AVG, for a 5.3% deficit to the i5-8400 with the same memory speed as the 1600X, or close to tied at 2666MHz.

Project Cars 2 CPU Benchmarks – i5-8400

i5 8400 pcars 1080p

In Project Cars at 1080p, the i5-8400 shows some more significant memory performance scaling than in other titles. We’re at 105FPS AVG with 3200MHz memory, but drop to about 95FPS AVG with 2666MHz. That’s a drop of about 9%, where we see about 4-5% in other titles. In terms of scaling, the 8400 offers functionally equivalent performance ot the i7-8700K stock, when both are at 3200MHz. It seems that this particular title is more frequency intensive, as are most, and that the limited boost speed of the 8700K when under high core engagement means it suffers a lower clock. We think you’d actually be better off by locking the 8700K to fewer cores for this game, then running a higher boost. The 8700K pulls significantly ahead when overclocked, as expected, and the same would be true if running a 4.7GHz boost – which we weren’t here, as enough cores engage to limit to around 4.3-4.4GHz.

i5 8400 pcars 1440p

At 1440p, it’s more of the same: The i5-8400 outputs about the same performance as previously, minus a couple frames at 3200MHz, because it is the bottleneck. Scaling and differences diminish between CPUs at this resolution.

GTA V CPU Benchmark – i5-8400

GTA V has generally shown poor favor to AMD, so think of this as one of the worst-case gaming results for Ryzen CPUs. Other games we tested, like Ashes, better benefit from the cores.

i5 8400 gtav 1080p

For GTA V at 1080p, the i5-8400 CPU with 3200MHz memory performs at 124FPS AVG, with lows at 93 and 86. This places the 8400 slightly ahead of the stock 7600K with equivalent memory speeds, with the 7600K behind by about 1.6%. This is just outside of standard deviation for us. Using 2666MHz memory, the i5-8400 places about 3.2% below the i5-7600K, or about 4.7% behind the unit with our standardized test speed of 3200MHz.

As for comparison against the flagship Coffee Lake CPU, the i5-8400 operates about 15% behind the i7-8700K, consistent with some previous tests. We also position well against the 4.1GHz overclocked R5 1600X, which operates around 107FPS AVG. This is consistent with past scoring for Ryzen in GTA V, and reflects an engine-level or game-level disconnect between the CPU and software.

i5 8400 gtav 1440p

At 1440p, some of the results compact closer to one another, now faced with other limitations in the pipe.  The i5-8400 is now 6% behind the i7-8700K when both are using 3200MHz memory, rather than 15% previously. The R5 1600X operates roughly the same average as before, given that we are faced with a CPU bottleneck.

Ashes of the Singularity CPU Benchmark – i5-8400

i5 8400 aots 1080p

Ashes remains one of the only benchmarks that really digs deep with DirectX 12 optimization and multi-core performance. The game ranks the i5-8400 at about 35FPS for 1080p/High, or 33 with 2666MHz. This outranks the overclocked i5-7600K when both are at 3200MHz, which speaks to the importance of cores in this test, as opposed to frequency demand in other tests. Naturally, this translates well for Ryzen: AMD’s 1600X doesn’t have much problem outperforming the i5-8400 in Ashes.


Intel’s i5-8400 CPU doesn’t seem to want to stick at a fixed price – we’ve seen it bounce up and down with launch, though not as violently as the i7-8700K (which is gouged beyond belief at some retailers, like Microcenter). The i5-8400 has bounced about +/-$10 in recent days, generally moving between $190 USD and $200 USD. At $190, it is a head-to-head comparison with the R5 1500X. In gaming, the i5-8400 outperforms the R5 1500X in most use cases. The i5-8400 also holds an advantage, by way of clock speed, in some production tests – like Blender. That said, the R5 1600/X offers significant performance uplift in those same production tests and, if Blender rendering on CPUs is really your thing, you’d be far better served by spending the extra $20 to $40 on the 1600 or 1600X. An i5-8400 is more suitable to a gaming machine, and that means that most of its owners will also own reasonable GPUs. GPUs can double as a CUDA workhorse, and it’s likely that mid-range or better GPUs would outperform the i5-8400 in render tasks where GPU acceleration exists. In shorter words: We’d generally advise not buying the i5 for rendering, despite reasonable performance versus the price-comparable R5 1500X. The R7 and 6C R5 CPUs make far more sense for that type of workload, or the i7-8700K, of course, though it’s never in stock.

As for gaming, the i5-8400 does quite well. Intel’s additional two cores favor the i5-8400 in thread-limited scenarios, but permit the high clock speeds we’ve come to know over the last few generations. These clock speeds are what contribute to advantages in games like Civilization VI, where we see greater turn time reductions from the clock than the cores (this is best illustrated by looking at R5 & KBL i5 overclock vs. stock metrics, where the overclocks assist more than anything else).

We still don’t have a full picture for this generation of Intel CPUs. Once we’ve gotten through the i3s and other i5s, we should better know which make the most sense at each price-point, and which become embattled with AMD at each price. For now, the i5-8400 performs reasonably and exhibits +/-5-7% performance swings from memory speed differences (3200MHz vs. 2666MHz) in most games, but we’d advise waiting. It doesn’t make any sense at all to buy a Z-series motherboard – the only 300-series boards presently out – with a locked i5 CPU; at least, not unless you’re planning to buy a K-SKU part later.

The i5-8400 holds much promise, even in thread-thrashing production loads (versus the previous Kaby Lake generation), but we want B/H boards to ship before making a hard recommendation.

Editorial, Test Lead: Steve Burke
Test Execution: Patrick Lathan
Video: Andrew Coleman

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Last modified on October 15, 2017 at 9:37 pm
Steve Burke

Steve started GamersNexus back when it was just a cool name, and now it's grown into an expansive website with an overwhelming amount of features. He recalls his first difficult decision with GN's direction: "I didn't know whether or not I wanted 'Gamers' to have a possessive apostrophe -- I mean, grammatically it should, but I didn't like it in the name. It was ugly. I also had people who were typing apostrophes into the address bar - sigh. It made sense to just leave it as 'Gamers.'"

First world problems, Steve. First world problems.

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