Core i3-1125G4 vs Core i5-8400

PassMark CPU Mark evaluates processor speed through complex mathematical computations. It provides a reliable metric to compare multi-core performance, where higher scores indicate faster processing for multitasking, gaming, and heavy workloads.

Core i3-1125G4 vs Core i5-8400 FPS Benchmarks

Predicted gaming performance across popular games. Tested paired with GeForce RTX 5090 to isolate CPU performance.

Search any supported game below to compare 1080p FPS for both components.

Core i3-1125G4 vs Core i5-8400: Pros, Cons & Final Verdict

See where each CPU makes more sense in practice: gaming, heavier work, platform cost, power draw, and upgrade path.

Core i3-1125G4

2021

Why buy it

✅+0.6% higher PassMark.
✅Draws 15W instead of 65W, a 50W reduction.

Trade-offs

❌Fewer obvious downsides in this matchup outside of normal market pricing swings.

Core i5-8400

2017

Why buy it

Trade-offs

❌Lower PassMark (9,229 vs 9,284).
❌Launch MSRP is still $182 MSRP, while Core i3-1125G4 mostly shows up through inconsistent older-market listings.
❌333.3% higher power demand at 65W vs 15W.

Quick Answers

So, is Core i3-1125G4 better than Core i5-8400?

It depends on what you want from the system. For gaming, Core i5-8400 is ahead with a 0.8% average FPS lead across 50 shared CPU game tests in our data. For rendering, compiling, streaming, and heavier multitasking, Core i3-1125G4 pulls ahead with 0.6% better PassMark.

Which one is better for streaming, content creation, and heavy multitasking?

For streaming, content creation, and heavier multitasking, Core i3-1125G4 is the stronger fit. You are getting 0.6% better PassMark, backed by 4 cores and 8 threads.

Which one is the smarter buy today, not just the cheaper CPU?

Core i3-1125G4 is still the much better call for a fresh build. Core i3-1125G4 comes in at an unclear MSRP at unclear MSRP versus $182 MSRP, and it still gives you 0.6% better PassMark. Core i5-8400 only looks stronger on raw value math because it is extremely cheap, but that usually means used-market pricing on an obsolete 2017 platform. Even with 100.0% better value on paper (50.7 vs 0.0 PassMark/$), it really only makes sense as a cheap stopgap or a niche existing-platform option for someone already on LGA1151.

Which one is more future-proof for 2026 and beyond?

Core i3-1125G4 makes more sense long term for 2026 and beyond. You are getting a newer CPU generation (2021 vs 2017) and more multi-core headroom with 4 cores / 8 threads instead of 6/6. That extra compute headroom is more likely to matter as games, background tasks, and creator workloads get heavier.

Core i3-1125G4 vs Core i5-8400 Technical Specifications

Side-by-side specs, architecture details, clocks, memory, power, and platform differences.

Core i3-1125G4

The Core i3-1125G4 is manufactured by Intel. It was released in 31 March 2021 (4 years ago). It is based on the Tiger Lake-UP3 (2020−2021) architecture. It features 4 cores and 8 threads. Base frequency is 2 GHz, with boost up to 3.7 GHz. L3 cache: 8 MB (total). L2 cache: 1.25 MB (per core). Built on 10 nm SuperFin process technology. Socket: FCBGA1449. Thermal design power (TDP): 15 Watt. Memory support: DDR4. Passmark benchmark score: 9,284 points. Launch price was $281.

Core i5-8400

The Core i5-8400 is manufactured by Intel. It was released in 5 October 2017 (8 years ago). It is based on the Coffee Lake-S (2017−2018) architecture. It features 6 cores and 6 threads. Base frequency is 2.8 GHz, with boost up to 4 GHz. L3 cache: 9 MB (total). L2 cache: 256K (per core). Built on 14 nm process technology. Socket: LGA1151. Thermal design power (TDP): 65 Watt. Memory support: DDR3, DDR4. Passmark benchmark score: 9,229 points. Launch price was $182.

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Processing Power

The Core i3-1125G4 packs 4 cores / 8 threads, while the Core i5-8400 offers 6 cores / 6 threads — the Core i5-8400 has 2 more cores. Boost clocks reach 3.7 GHz on the Core i3-1125G4 versus 4 GHz on the Core i5-8400 — a 7.8% clock advantage for the Core i5-8400 (base: 2 GHz vs 2.8 GHz). The Core i3-1125G4 uses the Tiger Lake-UP3 (2020−2021) architecture (10 nm SuperFin), while the Core i5-8400 uses Coffee Lake-S (2017−2018) (14 nm). In PassMark, the Core i3-1125G4 scores 9,284 against the Core i5-8400's 9,229 — a 0.6% lead for the Core i3-1125G4. L3 cache: 8 MB (total) on the Core i3-1125G4 vs 9 MB (total) on the Core i5-8400.

Feature	Core i3-1125G4	Core i5-8400
Cores / Threads	4 / 8	6 / 6+50%
Boost Clock	3.7 GHz	4 GHz+8%
Base Clock	2 GHz	2.8 GHz+40%
L3 Cache	8 MB (total)	9 MB (total)+13%
L2 Cache	1.25 MB (per core)	256K (per core)+20380%
Process	10 nm SuperFin-29%	14 nm
Architecture	Tiger Lake-UP3 (2020−2021)	Coffee Lake-S (2017−2018)
PassMark	9,284	9,229
Cinebench R23 Multi	5,112	—
Geekbench 6 Single	1,560	—
Geekbench 6 Multi	4,770	—

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Memory & Platform

The Core i3-1125G4 uses the FCBGA1449 socket (PCIe 4.0), while the Core i5-8400 uses LGA1151 (PCIe 3.0) — making them incompatible on the same motherboard. Maximum memory speed reaches DDR4-3200 on the Core i3-1125G4 versus DDR4-2666 on the Core i5-8400 — the Core i3-1125G4 supports 20% faster memory, which can translate to measurable gains in memory-sensitive workloads. The Core i5-8400 supports up to 128 GB of RAM compared to 64 GB — 100% more capacity for professional workloads. Both feature 2-channel memory with ECC support. Both provide 16 PCIe lanes. Chipset compatibility: SoC (Core i3-1125G4) and Intel 300 series (Core i5-8400).

Feature	Core i3-1125G4	Core i5-8400
Socket	FCBGA1449	LGA1151
PCIe Generation	PCIe 4.0+33%	PCIe 3.0
Max RAM Speed	DDR4-3200+20%	DDR4-2666
Max RAM Capacity	64 GB	128 GB+100%
RAM Channels	2	2
ECC Support	No	No
PCIe Lanes	16	16

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Advanced Features

Neither processor supports overclocking. Only the Core i3-1125G4 supports AVX-512 instructions — important for machine learning and scientific applications. Virtualization support: VT-x, VT-d, EPT (Core i3-1125G4) vs VT-x, VT-d (Core i5-8400). Both include integrated graphics — UHD Graphics (48 EU) (Core i3-1125G4) and UHD Graphics 630 (Core i5-8400) — useful as a fallback for troubleshooting or display output without a dedicated GPU. Primary use case: Core i3-1125G4 targets Productivity, Core i5-8400 targets Desktop. Direct competitor: Core i3-1125G4 rivals Ryzen 3 5300U.

Feature	Core i3-1125G4	Core i5-8400
Integrated GPU	Yes	Yes
IGPU Model	UHD Graphics (48 EU)	UHD Graphics 630
Unlocked	No	No
AVX-512	Yes	No
Virtualization	VT-x, VT-d, EPT	VT-x, VT-d
Target Use	Productivity	Desktop