i5-8400 vs Ryzen 9 3900X
Full specification comparison between the Intel Core i5-8400 (2017) and the AMD Ryzen 9 3900X (2019).
i5-8400
Intel Entry-level
- ✓ Has integrated graphics
- ✓ Lower power draw (65 W vs 105 W)
- ✓ Cheaper at launch ($182 vs $499)
- ✓ Better performance per dollar
Ryzen 9 3900X
AMD Entry-level
- ✓ ~23% faster on average
- ✓ More cores (12 vs 6)
- ✓ Larger L3 cache (64 MB vs 9 MB)
- ✓ Higher boost clock (4.6 vs 4.0 GHz)
- ✓ Newer (2019 vs 2017)
Verdict: The Ryzen 9 3900X is roughly 23% faster than the i5-8400 on average — a clear, noticeable performance advantage.
Note they use different platforms (AM4 vs LGA1151), so this is a motherboard decision too, not just a CPU swap.
At launch pricing, the i5-8400 offers more performance per dollar, and the i5-8400 is the more power-efficient chip.
Estimated performance
Estimated average 1080p gaming performance compiled from publicly available benchmark data. Individual games vary.
Specs side by side
| Specification | i5-8400 | Ryzen 9 3900X |
|---|---|---|
| Family | Coffee Lake | Zen 2 |
| Socket | LGA1151 | AM4 |
| Release year | 2017 | 2019 |
| Est. gaming perf. | ||
| Est. multi-core perf. | ||
| Est. single-core perf. | ||
| Cores | ||
| Threads | ||
| Max boost clock | ||
| L3 cache | ||
| TDP (base) | ||
| Integrated graphics | UHD 630 | None |
| Launch MSRP |
Green bars mark the better value in each row (for power and price, lower wins).
Frequently asked questions
Is the Ryzen 9 3900X better than the i5-8400?
Yes — based on aggregated benchmark data, the Ryzen 9 3900X is about 23% faster than the i5-8400 on average.
How much faster is the Ryzen 9 3900X than the i5-8400?
Roughly 23% on average in gaming workloads. The gap varies by title, resolution and settings.
Which processor is better value?
Comparing launch prices, the i5-8400 delivers more performance per dollar. Check current street prices, as market pricing often shifts the value equation.