I ran FreshDiagnose on a computer, and I can't tell if it supports 64-bit instructions. It says the data bus width is 64-bit, but I'm not sure what that means. Here is the output.
Code:Processor This module contains information about your computer's central processor(s) and its capabilities. Processor Model Intel Pentium 4 Type Primary Processor Vendor Intel Corporation Family Intel P4 Family Hardcoded Name Intel(R) Xeon(TM) CPU 3.00GHz Frequency 2992 MHz Family/Model/Stepping 15/4/3 Logical CPU Count 2 Apic ID 6 CL Flush 8 Detailed Info Address Bus Width 36 Bit Core Details 126 µOPs, 48 Loads, 24 Stores In-Flight Data Bus Width 64 Bit Execution Speed Up to 6 µOPs/Cycle Execution Units Double-pumped ALU, FP Move/Store/FXCH, Double-pumped ALU, Slow ALU, FP Execute, Load, Store Floating Point Integrated Instruction Decoder 1x IA-32/Cycle Instruction Set IA-32 Multimedia MMX, SSE, SSE2 Multiprocessing SMP, using integrated local xAPICs Physical Memory 2^36 Bit (64 GB) Pipeline Depth 20 Stages Power Management HLT, STPCLK, SMI/SMM, Sleep, Deep Sleep, Automatic Clock Throttling Processor Core RISC, Out-of-order and Speculative Execution Processor Modes Real, Protected, Virtual, Paging, SMM, Probe Mode Registers 32 Bit Integer, 80 Bit FP, 64 Bit MM, 128 Bit SSE and SSE2 Split Voltage Yes (Automatically determined via VID Pins) Supported External Bus Speed 100, 133 MHz Quad-Pumped, AGTL+ Supported Multiplier 13.0x, 14.0x, ..., 24.0x Virtual Memory 65,528 GB (~64 TB) Cache Configuration L1 Code TLB 4 KB pages, 4-way set associative, 32 entries 4 KB/4 MB/2 MB pages, fully associative, 64 entries L1 Data TLB 4 KB/4 MB pages, fully associative, 64 entries L2 Cache None Trace L1 Cache 12 KµOPs, 8-way set associative Processor Features Floating-point Unit on chip (FPU) Yes MMX Instructions (MMX) Yes MMX Instruction Extensions (MMX+) No 3DNow! Instructions No 3DNow! Instruction Extensions (3DNow!+) No Streaming SIMD Extensions (SSE) Yes Streaming SIMD Extensions 2 (SSE2) Yes Multiprocessor Capable No x86-64 Long Mode (LM) Yes Virtual Mode Extension (VME) Yes Debugging Extension (DE) Yes Page Size Extension (PSE) Yes Time Stamp Counter (TSC) Yes Model Specific Registers (MSR) Yes Physical Address Extension (PAE) Yes Machine Check Exception (MCE) Yes CMPXCHG8 Instruction (CX8) Yes On-chip APIC Hardware (APIC) Yes Fast System Call (SEP) Yes Memory Type Range Registers (MTRR) Yes Page Global Enable (PGE) Yes Machine Check Architecture (MCA) Yes Conditional Move Instruction (CMOV) Yes Page Attribute Table (PAT) Yes 36-bit Page Size Extension (PSE36) Yes 96-bit Processor Number (PSN) No CLFLUSH Instruction (CLFSH) Yes Debug Trace Store (DTS) Yes ACPI Supported (ACPI) Yes Fast Save and Restore (FXSR) Yes Self Snoop (SS) Yes Thermal Monitor Supported (TM) Yes IA-64 Processor Capable (IA-64) No