When to use 64 Bit programs

• Need to use a library that has only a 64 bit version
• Need to use more than 4 gigabytes of virtual address space
• Needs full 64 bit registers to do efficient 64-bit arithmetic
• Uses files larger than 2 gigabytes

Major Differences Between 32 and 64 Programs

• 32-bit: longs and pointers are 32 bits
• 64-bit: longs and pointers are 64 bits

Types of Applications that Can Benefit from 64 bit Environment with Larger Primary Memory

• programs that access large data bases
• large CAD/CAE models and simulations
• larger scientific computing problems
• web caches can hold more in memory, reducing latency

In a 64-bit environment

• process can have up to 64-bits of virtual address - 18 exabytes
• compilers have options for using 32 and 64 bit programs