Intel Knights Mill

GCC 15 removed -march=knm.

Product lines

The product lines built on Knights Mill, with the market segment the vendor sells each in and the sockets or soldered (BGA) packages its processors come in. Each socket links to the vendor page that states it.

Product line	Segment	Socket	Source
Xeon Phi 72x5	server	LGA3647 (Xeon Phi)	intel.com

Why not x86-64-v4?

Knights Mill lacks AVX512BW, AVX512DQ and AVX512VL, all of which x86-64-v4 requires.

Feature checklist

Features required by each x86-64 level and whether Knights Mill has them. OSFXSR and OSXSAVE are set by the operating system; the table checks the hardware features they depend on.

Feature	Knights Mill	Enumerated by	Linux flag
x86-64-v1
CMOV	Yes	`CPUID.01H:EDX[15]`	`cmov`
CX8	Yes	`CPUID.01H:EDX[8]`	`cx8`
FPU	Yes	`CPUID.01H:EDX[0]`	`fpu`
FXSR	Yes	`CPUID.01H:EDX[24]`	`fxsr`
MMX	Yes	`CPUID.01H:EDX[23]`	`mmx`
OSFXSR via FXSR	Yes	`CPUID.01H:EDX[24]`	`fxsr`
SCE	Yes	`CPUID.80000001H:EDX[11]`	`syscall`
SSE	Yes	`CPUID.01H:EDX[25]`	`sse`
SSE2	Yes	`CPUID.01H:EDX[26]`	`sse2`
x86-64-v2
CMPXCHG16B	Yes	`CPUID.01H:ECX[13]`	`cx16`
LAHF-SAHF	Yes	`CPUID.80000001H:ECX[0]`	`lahf_lm`
POPCNT	Yes	`CPUID.01H:ECX[23]`	`popcnt`
SSE3	Yes	`CPUID.01H:ECX[0]`	`pni`
SSE4.1	Yes	`CPUID.01H:ECX[19]`	`sse4_1`
SSE4.2	Yes	`CPUID.01H:ECX[20]`	`sse4_2`
SSSE3	Yes	`CPUID.01H:ECX[9]`	`ssse3`
x86-64-v3
AVX	Yes	`CPUID.01H:ECX[28]`	`avx`
AVX2	Yes	`CPUID.(EAX=07H,ECX=0):EBX[5]`	`avx2`
BMI1	Yes	`CPUID.(EAX=07H,ECX=0):EBX[3]`	`bmi1`
BMI2	Yes	`CPUID.(EAX=07H,ECX=0):EBX[8]`	`bmi2`
F16C	Yes	`CPUID.01H:ECX[29]`	`f16c`
FMA	Yes	`CPUID.01H:ECX[12]`	`fma`
LZCNT	Yes	`CPUID.80000001H:ECX[5]`	`abm`
MOVBE	Yes	`CPUID.01H:ECX[22]`	`movbe`
OSXSAVE via XSAVE	Yes	`CPUID.01H:ECX[26]`	`xsave`
x86-64-v4
AVX512F	Yes	`CPUID.(EAX=07H,ECX=0):EBX[16]`	`avx512f`
AVX512BW	No	`CPUID.(EAX=07H,ECX=0):EBX[30]`	`avx512bw`
AVX512CD	Yes	`CPUID.(EAX=07H,ECX=0):EBX[28]`	`avx512cd`
AVX512DQ	No	`CPUID.(EAX=07H,ECX=0):EBX[17]`	`avx512dq`
AVX512VL	No	`CPUID.(EAX=07H,ECX=0):EBX[31]`	`avx512vl`

Other extensions

Notable extensions outside the x86-64 levels. Vendors sometimes disable these on individual models. Linked names lead to the extension's instructions.

AES-NI
PCLMULQDQ
RDRAND
RDSEED
ADX
AVX512-VPOPCNTDQ

Known vulnerabilities

The CVEs that the sources of the vulnerability list name as affecting Knights Mill, in all of its models or in some of them.

CVE-2018-12126 Microarchitectural Data Sampling: Microarchitectural Store Buffer Data Sampling
CVE-2017-5754 Meltdown: Rogue Data Cache Load
CVE-2017-5753 Spectre variant 1: Bounds Check Bypass
CVE-2017-5715 Spectre variant 2: Branch Target Injection

Knights Landing 2016 v3
Knights Mill 2017 v3

Product lines

Why not x86-64-v4?

Feature checklist

Other extensions

Known vulnerabilities

Other Intel Xeon Phi microarchitectures

Sources