SixtyFour lists apps that will open in 64-bit mode and facilitates the changing of a preference to force the apps to open in 32-bit mode.
An application opened in 64-bit mode uses approximately 2x the memory that the same application uses when opened in 32-bit mode. Forcing an application to open in 32-bit mode eliminates the additional memory overhead. Eliminating the additional memory overhead could lead to a increase in overall system performance especially on older systems that have little memory available.
