BMI2 Instruction Not Supported on Intel J4125 (Goldmont Plus)

[PeterSuh-Q3]

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name: BMI2 Instruction Not Supported on Intel J4125 (Goldmont Plus)
about: Document CPU instruction set limitation for J4125-based systems
labels: hardware, compatibility, cpu

Summary

Intel Celeron J4125 does not support the BMI2 (Bit Manipulation Instruction Set 2) instruction set. Running binaries that depend on BMI2 will result in a SIGILL (Illegal Instruction) crash on J4125-based systems.

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Environment

Property	Value
CPU	Intel Celeron J4125
Platform	Gemini Lake Refresh
Microarchitecture	Goldmont Plus (Atom family)
Process Node	14nm
Release	Q4 2019
TDP	10W

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Problem Description

The J4125 is based on Intel's Goldmont Plus microarchitecture, which belongs to the low-power Atom family. This architecture does not include BMI1 or BMI2 support, nor does it support AVX/AVX2 or FMA3.

Any software compiled with -mbmi2 or that relies on runtime CPU feature detection for BMI2 (e.g., BZHI, MULX, PDEP, PEXT, RORX, SARX, SHRX, SHLX) will immediately crash on this platform.

Confirmed Unsupported Instructions

BZHI, MULX, PDEP, PEXT, RORX, SARX, SHRX, SHLX

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Instruction Set Support Matrix (J4125 / Goldmont Plus)

Instruction Set	Supported
SSE / SSE2 / SSE3 / SSSE3	✅
SSE4.1 / SSE4.2	✅
AES-NI	✅
PCLMUL	✅
SHA	✅
RDRAND / RDSEED	✅
AVX / AVX2	❌
BMI1	❌
BMI2	❌
FMA3	❌

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Intel Atom Microarchitecture — BMI2 Support Timeline

BMI2 support was introduced in the Atom family starting with Tremont (2020):

Microarchitecture	Platform	BMI2
Silvermont (2013)	Z3xxx, J1xxx, N2xxx	❌
Airmont (2015)	Z8xxx, x5/x7	❌
Goldmont (2016)	J3xxx, N3xxx (Apollo Lake)	❌
Goldmont Plus (2017–2019)	J4xxx, N4xxx (Gemini Lake)	❌
Tremont (2020)	J6xxx, N6xxx (Jasper/Elkhart Lake)	✅
Gracemont (2021+)	N100, N200, N305, Alder Lake E-core	✅

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Impact

• Software with hard BMI2 dependency (e.g., InfluxDB v3, some compression libraries) will fail to start on J4125-based systems.
• This affects many embedded/NAS devices (e.g., Synology, QNAP, industrial mini-PCs) using the J4125.
• There is no workaround at the software level without recompiling without BMI2 support.

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Suggested Fix / Workaround

• Runtime detection: Check CPU feature flags (/proc/cpuinfo → bmi2) before executing BMI2-dependent code paths.
• Graceful fallback: Provide a non-BMI2 code path for systems that do not expose the bmi2 flag.
• Hardware upgrade: If BMI2 is strictly required, upgrade to a platform using Tremont (e.g., N5105, J6412) or Gracemont (e.g., N100, N200) which fully support BMI2.

Check BMI2 availability at runtime (Linux)

grep -o 'bmi2' /proc/cpuinfo | head -1
# Empty output = BMI2 NOT supported (e.g., J4125)
# "bmi2"       = BMI2 IS supported

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References

• Intel Celeron J4125 Official Specifications
• Goldmont Plus Microarchitecture — Wikipedia
• x86 Bit Manipulation Instruction Set — Wikipedia

[PeterSuh-Q3]

Does Intel 4th Gen (Haswell) Fully Support BMI2?

Short answer: No. While BMI2 was indeed introduced with the Haswell (4th Gen) microarchitecture, not all SKUs within the 4th generation support BMI2. [web:41][web:8]

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BMI2 Exceptions Within Haswell

Even within the 4th Gen Haswell family, BMI2 support depends on the brand tier. [web:41][web:8]

• Desktop (Haswell-S) Pentium / Celeron grade → ❌ BMI2 NOT supported [web:41]
• Desktop (Haswell-S) Core i3 and above → ✅ BMI2 supported [web:41]
• High-performance Mobile (Haswell-H) → ✅ BMI2 supported [web:41]

In other words, even within the same generation, BMI2 support varies by product tier. [web:41]

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BMI2 Support by Generation

Generation / Architecture	BMI2 Support
3rd Gen and below (Ivy Bridge and earlier)	❌ [web:8]
4th Gen Haswell — Core i3 and above	✅ [web:41]
4th Gen Haswell — Pentium / Celeron	❌ [web:41]
5th Gen Broadwell and above (Core series)	✅ (most SKUs) [web:8]
Atom Goldmont Plus and below (incl. J4125)	❌ [web:16]
Atom Tremont and above (N5105, J6412, etc.)	✅ [web:30]

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Key Principle

Intel states that BMI2 support is determined by the microarchitecture, not simply by the brand name. [web:8] Therefore, instead of relying only on the generation number, you should verify support using the official CPU specification page or by checking the target system directly. [web:8]

grep -o 'bmi2' /proc/cpuinfo | head -1
# Empty output = BMI2 NOT supported
# "bmi2"       = BMI2 IS supported

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References

• Intel ARK — Celeron J4125 Specifications
• Intel Support — Does Intel® Xeon® Processor Family Support BMI2?
• Goldmont Plus Microarchitecture — Wikipedia
• x86 Bit Manipulation Instruction Set — Wikipedia