Quick Verdict
A highly cost-effective 6-core processor that delivers excellent value for mainstream users, though lacking Hyper-Threading limits its heavy multitasking ceiling.
Overview
Launch
Sep 1st, 2018
Status
End-of-lifeGeneration
Core i5 (Coffee Lake)
Market
Desktop
The Intel Core i5-8420 is a mainstream six-core desktop processor that quietly filled the gaps in Intel's 8th Generation Coffee Lake lineup, offering a compelling mix of clock speeds and core counts for budget-conscious users.
The Core i5-8420 delivers 6 physical cores operating up to 4.1 GHz, paired with UHD Graphics 630. It became a staple for budget builders, offering enough single-core speed for modern games and daily tasks without breaking the bank.
Specifications
Performance
Handles office tasks and moderate programming workloads efficiently.
Good for basic VMs, but 6 threads limit heavy parallel virtualization.
Capable of smooth 1080p gaming when paired with a mid-range discrete GPU.
Balanced performance within a standard 65W power envelope.
- •Excellent for budget gaming builds
- •Handles eSports titles flawlessly
- •May bottleneck high-end modern GPUs at 1080p
- •No AI-specific hardware
- •CPU inference is slow due to lack of threads
Architecture
14 nm
Process Node
Coffee Lake
Codename
6C / 6T
Core Config
9 MB
L3 Cache
65 W
TDP
Architecture Overview
Architecturally, the Core i5-8420 shares the identical Coffee Lake 14nm design as the rest of the 8th Gen i5 family. It utilizes a ring bus topology to connect the six physical cores to the 9MB L3 SmartCache, optimizing latency for gaming workloads. Because it lacks Hyper-Threading, each core processes a single thread, relying on high clock speeds—up to 4.1 GHz—to maintain instruction throughput. The processor supports dual-channel DDR4-2666 memory natively, which pairs adequately with mid-range discrete GPUs to prevent memory bottlenecks. Intel's 14nm process was highly mature by this point, allowing the 8420 to hit strong sustained boost clocks without exceeding the 65W thermal limit. The integrated UHD Graphics 630 features 24 Execution Units and handles hardware decoding for modern video formats. The processor also retains full support for advanced instruction sets, including AVX2, SSE4.2, and AES-NI, ensuring robust performance in cryptographic and vector-heavy tasks.
CPU Design
6 cores, 6 threads (no Hyper-Threading).
Memory Subsystem
Dual-channel DDR4-2666.
PCIe & I/O
16 PCIe 3.0 lanes.
Overclocking
Locked multiplier.
- Two additional physical cores
- Higher maximum turbo frequency
Key Highlights
- Excellent price-to-performance ratio historically
- Strong single-core speeds for gaming
- Includes integrated UHD Graphics 630
- Standard 65W TDP is easy to cool
- Wide compatibility with 300-series motherboards
- No Hyper-Threading (only 6 threads)
- Locked multiplier prevents overclocking
- End-of-life platform (LGA 1151)
- Officially limited to DDR4-2666
- Not supported by Windows 11 officially
History
Released on September 1st, 2018, the Core i5-8420 emerged as a minor refresh within the Coffee Lake family, likely serving to optimize silicon yields or fulfill specific OEM pricing requirements. By late 2018, the 8th Generation lineup had firmly established Intel's dominance in the mainstream market against AMD's Ryzen 5 offerings. The 8420 was a quiet release, often found in pre-built systems from major OEMs rather than heavily marketed to DIY builders.
It represented Intel's strategy of saturating the budget and mid-range market with varied SKUs to cater to highly specific price points. While it didn't generate the massive hype of the initial 8400 launch, the 8420 solidified the standard for 6-core processing in the sub-$200 segment. It acted as a stopgap, keeping the Coffee Lake architecture relevant in the budget sector while Intel prepared its 9th Generation Refresh.
Improvements over Previous Generation
- Two additional physical cores
- Higher maximum turbo frequency
Alternatives & Competitors
Should You Buy It?
Recommended for the right buyer
Upgrading an older LGA 1151 system on a budget, or building an office/HTPC machine.
Avoid if…
- Building a new PC from scratch (newer platforms offer better value)
- Doing heavy 3D rendering or video editing
- Requiring high-refresh-rate gaming with top-tier GPUs
Use Cases
Interesting Facts
The i5-8420 was often found in pre-built OEM systems rather than the DIY market.
It features a max turbo boost of 4.1 GHz on single-core workloads.
Includes Intel UHD Graphics 630, allowing it to function without a dedicated GPU.
Uses the FC-LGA1151 package and part number SR3X4.
Shares the exact same die as the i5-8400 but with slightly higher clocks.
Officially supports DDR4-2666 memory in dual-channel mode.
The 8th Gen i5 lineup permanently moved Intel's mainstream i5 tier to 6 cores.
Features 16 PCIe 3.0 lanes for direct GPU and NVMe connectivity.
Has a base clock of 2.9 GHz and a 100 MHz base bus speed.
Can run Windows 11 despite lacking official support.
People Also Ask
Is the Intel Core i5-8420 good for gaming?
Yes, it is still capable for 1080p budget gaming when paired with a mid-range GPU.
Does the i5-8420 have Hyper-Threading?
No, it has 6 physical cores but only 6 threads, meaning no Hyper-Threading.
Can you overclock the i5-8420?
No, the multiplier is locked. Only BCLK overclocking is possible on certain motherboards, which is not recommended.
What is the max turbo frequency of the i5-8420?
The maximum turbo frequency is 4.1 GHz.
Does the i5-8420 have integrated graphics?
Yes, it includes the Intel UHD Graphics 630.
What socket does the i5-8420 use?
It uses the Intel Socket 1151 (LGA 1151).
What RAM speed does the i5-8420 support?
It officially supports DDR4-2666 memory in dual-channel mode.
Does the i5-8420 support Windows 11?
Officially no, but it can run Windows 11 via registry workarounds.
What is the TDP of the i5-8420?
The standard TDP is 65 Watts.
Does the i5-8420 come with a cooler?
Yes, retail boxed versions include a standard Intel stock cooler.
Frequently Asked Questions
What is the difference between i5-8400 and i5-8420?
The i5-8420 has a 100 MHz higher base clock (2.9 GHz vs 2.8 GHz) but otherwise shares identical architecture and turbo speeds.
Can the i5-8420 run 4K video?
Yes, it can decode and play 4K video smoothly using the integrated UHD Graphics 630.
What motherboards support the i5-8420?
It is compatible with Intel 300-series chipset motherboards (Z390, B360, H310, etc.).
Does the i5-8420 support PCIe 4.0?
No, it only supports PCIe 3.0.
What is the cache size of the i5-8420?
It has a 9 MB L3 SmartCache.
Is the i5-8420 good for streaming?
It can handle basic streaming, but the lack of threads may cause stuttering in CPU-heavy games.
What is the base clock of the i5-8420?
The base clock is 2.9 GHz.
Can the i5-8420 run AutoCAD?
Yes, it is perfectly capable of running 2D AutoCAD and moderate 3D modeling.
Does the i5-8420 support ECC memory?
No, the i5-8420 does not support Error-Correcting Code (ECC) memory.
What is the part number for the i5-8420?
The part number is SR3X4.