Processors/Comparison
15 specifications
Intel Core i5-12400 vs Intel Core i7-8700K
On paper, the Intel Core i7-8700K boosts higher, and the Intel Core i5-12400 carries more L3 cache. Specifications describe what each chip is designed to do; how much of that either one holds under continuous load is a separate question.
Intel Core i5-12400
Intel · Core 12th generation · Desktop
Intel Core i7-8700K
Intel · Coffee Lake (8th gen) · Desktop
Cores and clocks
Cache and power
Platform
A check marks the higher figure only on rows where higher is unambiguously better. Rows without one are not ties; they are specifications where “better” has no meaning.
Reading the table
What the difference means.
Boost clock
The Core i7-8700K boosts to 4.7 GHz against 4.4 GHz, 7 percent higher. Across generations it is not a guide to speed on its own, for the reason above. Boost is also a peak: it is held for seconds to minutes, on one or two cores, while the cooling and the power limit allow. What either chip settles at under a long load is lower, and it depends on the cooler and the motherboard as much as the chip.
Cache
The Core i5-12400 carries 18 MB of L3 cache against 12 MB. Cache is fast memory on the chip, and a larger one means the cores wait on main memory less often. Games, large spreadsheets and compiling respond to it; rendering and video export, which stream through data in order, respond much less.
Power and cooling
The Core i7-8700K is rated at 95 W against 65 W. The rating is the heat the cooler has to move for the chip to hold its speed, and modern chips draw well above it in short bursts. A competent tower cooler suits the Core i7-8700K; the Core i5-12400 is easier to keep quiet and fits smaller cases. A chip whose cooling falls short does not fail. It slows down, and it does so after the first minute, which is why short benchmarks miss it.
Platform
They use different sockets, FCLGA1700 and FCLGA1151, so moving from one to the other means a new motherboard. For an upgrade, that cost belongs in the comparison; for a new build, the newer platform is the one with later chips still to come.
Which to pick, on paper
- A quiet or compact build
- Core i5-12400
- 65 W against 95 W: less heat to move, so a smaller cooler and slower fans.
What no table says
How much of its speed a processor keeps after the first minute depends on the cooling and the power limit of the machine it is in. If you own one of these, measure it: the test is free and runs in this browser.
Questions
- Is the Core i5-12400 better than the Core i7-8700K?
- By need, on the specifications: a quiet or compact build: the Core i5-12400. No specification says how much speed either one keeps under a long load; that depends on the cooling and the power limit of the machine it is in, and it is what a sustained test measures.
- Do the Core i5-12400 and the Core i7-8700K use the same socket?
- No. The Core i5-12400 uses FCLGA1700 and the Core i7-8700K uses FCLGA1151, so switching means a new motherboard.
- Does the Core i5-12400 or the Core i7-8700K have integrated graphics?
- Both do: Intel UHD Graphics 730 on the Core i5-12400 and Intel UHD Graphics 630 on the Core i7-8700K.
- Which runs hotter, the Core i5-12400 or the Core i7-8700K?
- The Core i7-8700K is rated at 95 W against 65 W, so it produces more heat under load and needs the larger cooler. How hot either one actually runs depends on the cooler and the case more than on the chip.
More comparisons
- Intel Core i5-12400 vs Intel Core i5-12400F
- Intel Core i5-12400 vs Intel Core i7-8700
- Intel Core i5-12400 vs Intel Core i5-9600K
- Intel Core i5-12400 vs Intel Core i5-10500
- Intel Core i5-12400 vs Intel Core i5-11400F
- Intel Core i7-8700K vs Intel Core i5-12500
- Intel Core i7-8700K vs Intel Core i7-8700
- Intel Core i7-8700K vs Intel Core i5-10600
- Intel Core i7-8700K vs Intel Core i5-12400F
- Intel Core i7-8700K vs AMD Ryzen 5 3600
Every figure on this table is a design target. None of it is a measurement.
Nothing above describes how a processor behaves twenty minutes into a sustained workload, which is where two chips with nearly identical specifications routinely diverge. A boost clock is a ceiling the vendor permits, not a rate the chip sustains, and whether it holds depends on the cooling, the case, the power profile and the room. None of those appear on a specification sheet.
We deliberately do not reduce these figures to a single score. A composite invented from specifications would look authoritative and measure nothing, and choosing the weights would be choosing the winner.