1) we need a little bit more info to confirm if Apple really release a new firmware with the exact same BootROM version number.
2) Did you ever dump and backup your 0085.B00 firmware? If yes, use ROMTool to flash that back into your Mac, then the latest installer will ask you to upgrade to 0087.B00 (the new one?) again.
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Just download the 10.13.5 full installer again, extracted the 0087.B00 from the installer, still no microcode in there.
Can you post a screenshot of your OS microcode confirmation with OS version and BootROM version please?
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I am with the PB, not DP.
The firmware still 0085.B00 in the latest PB (I downloaded that just 5min ago), and microcode version still 15.
machdep.cpu.max_basic: 11
machdep.cpu.max_ext: 2147483656
machdep.cpu.vendor: GenuineIntel
machdep.cpu.brand_string: Intel(R) Xeon(R) CPU W3680 @ 3.33GHz
machdep.cpu.family: 6
machdep.cpu.model: 44
machdep.cpu.extmodel: 2
machdep.cpu.extfamily: 0
machdep.cpu.stepping: 2
machdep.cpu.feature_bits: 188838921972218879
machdep.cpu.extfeature_bits: 5034215680
machdep.cpu.signature: 132802
machdep.cpu.brand: 0
machdep.cpu.features: FPU VME DE PSE TSC MSR PAE MCE CX8 APIC SEP MTRR PGE MCA CMOV PAT PSE36 CLFSH DS ACPI MMX FXSR SSE SSE2 SS HTT TM PBE SSE3 PCLMULQDQ DTES64 MON DSCPL VMX SMX EST TM2 SSSE3 CX16 TPR PDCM SSE4.1 SSE4.2 POPCNT AES PCID
machdep.cpu.extfeatures: SYSCALL XD 1GBPAGE EM64T LAHF RDTSCP TSCI
machdep.cpu.logical_per_package: 32
machdep.cpu.cores_per_package: 16
machdep.cpu.microcode_version: 31
machdep.cpu.processor_flag: 0
machdep.cpu.mwait.linesize_min: 64
machdep.cpu.mwait.linesize_max: 64
machdep.cpu.mwait.extensions: 3
machdep.cpu.mwait.sub_Cstates: 4384
machdep.cpu.thermal.sensor: 1
machdep.cpu.thermal.dynamic_acceleration: 1
machdep.cpu.thermal.invariant_APIC_timer: 1
machdep.cpu.thermal.thresholds: 2
machdep.cpu.thermal.ACNT_MCNT: 1
machdep.cpu.thermal.core_power_limits: 0
machdep.cpu.thermal.fine_grain_clock_mod: 0
machdep.cpu.thermal.package_thermal_intr: 0
machdep.cpu.thermal.hardware_feedback: 0
machdep.cpu.thermal.energy_policy: 0
machdep.cpu.arch_perf.version: 3
machdep.cpu.arch_perf.number: 4
machdep.cpu.arch_perf.width: 48
machdep.cpu.arch_perf.events_number: 7
machdep.cpu.arch_perf.events: 4
machdep.cpu.arch_perf.fixed_number: 3
machdep.cpu.arch_perf.fixed_width: 48
machdep.cpu.cache.linesize: 64
machdep.cpu.cache.L2_associativity: 8
machdep.cpu.cache.size: 256
machdep.cpu.tlb.inst.small: 64
machdep.cpu.tlb.inst.large: 7
machdep.cpu.tlb.data.small: 64
machdep.cpu.tlb.data.large: 32
machdep.cpu.tlb.shared: 512
machdep.cpu.address_bits.physical: 36
machdep.cpu.address_bits.virtual: 48
machdep.cpu.core_count: 6
machdep.cpu.thread_count: 12
machdep.cpu.tsc_ccc.numerator: 0
machdep.cpu.tsc_ccc.denominator: 0machdep.cpu.thread_count: 12
machdep.cpu.tsc_ccc.numerator: 0
machdep.cpu.tsc_ccc.denominator: 0