What is the equivalent of /proc/cpuinfo on FreeBSD v8.1?

I don’t believe there is anything as detailed as Linux’s /proc/cpuinfo. Look into sysctl hw and /var/run/dmesg.boot. Most of the information like CPU speed and instruction sets should be in there somewhere.

This is what I see (with a few uninteresting hw.* fields removed):

$ uname -sr
FreeBSD 4.10-RELEASE
$ grep -i cpu /var/run/dmesg.boot 
CPU: Pentium III/Pentium III Xeon/Celeron (448.97-MHz 686-class CPU)
$ /sbin/sysctl hw
hw.machine: i386
hw.model: Pentium III/Pentium III Xeon/Celeron
hw.ncpu: 1
hw.byteorder: 1234
hw.physmem: 665989120
hw.usermem: 604614656
hw.pagesize: 4096
hw.floatingpoint: 1
hw.machine_arch: i386
hw.aac.iosize_max: 65536
hw.an.an_dump: off
hw.an.an_cache_mode: dbm
hw.an.an_cache_mcastonly: 0
hw.an.an_cache_iponly: 1
hw.fxp_rnr: 0
hw.fxp_noflow: 0
hw.dc_quick: 1
hw.ste.rxsyncs: 0
hw.instruction_sse: 0
hw.availpages: 162432

(Note that on OpenBSD, the cpu speed is found in hw.cpuspeed instead of in dmesg.)

Use dmidecode command:

# dmidecode -t processor -t cache
# dmidecode 3.0
Scanning /dev/mem for entry point.
SMBIOS 2.4 present.

Handle 0x0004, DMI type 4, 35 bytes
Processor Information
        Socket Designation: LGA 775
        Type: Central Processor
        Family: Pentium 4
        Manufacturer: Intel
        ID: F6 06 00 00 FF FB EB BF
        Signature: Type 0, Family 6, Model 15, Stepping 6
        Flags:
                FPU (Floating-point unit on-chip)
                VME (Virtual mode extension)
                DE (Debugging extension)
                PSE (Page size extension)
                TSC (Time stamp counter)
                MSR (Model specific registers)
                PAE (Physical address extension)
                MCE (Machine check exception)
                CX8 (CMPXCHG8 instruction supported)
                APIC (On-chip APIC hardware supported)
                SEP (Fast system call)
                MTRR (Memory type range registers)
                PGE (Page global enable)
                MCA (Machine check architecture)
                CMOV (Conditional move instruction supported)
                PAT (Page attribute table)
                PSE-36 (36-bit page size extension)
                CLFSH (CLFLUSH instruction supported)
                DS (Debug store)
                ACPI (ACPI supported)
                MMX (MMX technology supported)
                FXSR (FXSAVE and FXSTOR instructions supported)
                SSE (Streaming SIMD extensions)
                SSE2 (Streaming SIMD extensions 2)
                SS (Self-snoop)
                HTT (Multi-threading)
                TM (Thermal monitor supported)
                PBE (Pending break enabled)
        Version: Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz
        Voltage: 1.4 V
        External Clock: 266 MHz
        Max Speed: 3800 MHz
        Current Speed: 2394 MHz
        Status: Populated, Enabled
        Upgrade: Other
        L1 Cache Handle: 0x0005
        L2 Cache Handle: 0x0006
        L3 Cache Handle: 0x0007
        Serial Number: To Be Filled By O.E.M.
        Asset Tag: To Be Filled By O.E.M.
        Part Number: To Be Filled By O.E.M.

Handle 0x0005, DMI type 7, 19 bytes
Cache Information
        Socket Designation: L1-Cache
        Configuration: Enabled, Not Socketed, Level 1
        Operational Mode: Write Back
        Location: Internal
......