Here is information on hardware capabilities. For a basic list of compatible hardware see "Hardware Notes" under http://www.freebsd.org/releases/ .
If the CPU is 32-bit, you can upgrade it to a 64-bit CPU if the motherboard is documented according to socket type, and CPU compatibility. This alone makes a big difference in computer performance.
Select Intel, Nvidia and Radeon graphics cards work with varying advanced capabilities with the production ready version of FreeBSD. Other graphics cards are compatible with FreeBSD, but unfortunately without their full abilities. For details of compatible capabilities of certain graphics cards see:
Type swapinfo -m at the command line to see how much swap in megabytes is used on a heavy process. Consider getting this amount of RAM if your motherboard is labeled enough to find documentation on the type of RAM it uses. Modern types of Desktop ram are DDR, DDR2, DDR3, and DDR4. Laptop RAM has a different version than Desktops.
Dual Channel RAM works faster than single channel RAM. The bus width for Dual channel RAM is double that of single channel RAM (128-bit instead of 64-bit), because two separate modules are acting as one using twice as many connections. In order for Dual Channel ram to work, identical Dual Channel RAM modules must be installed usually by skipping a RAM slot on the motherboard. The computer's Bios may confirm that Dual Channel is enabled on boot-up. For more details see: