The following outlines the minimum hardware requirements for pfSense 1.2. Note the minimum requirements are not suitable for all environments, see the Hardware Sizing Guidance page for information.

CPU - 100 MHz Pentium 
RAM - 128 MB

Requirements specific to individual platforms follow.  

Live CD
CD-ROM drive
USB flash drive or floppy drive to hold configuration file

Hard drive installation
CD-ROM for initial installation
1 GB hard drive

Embedded
128 MB Compact Flash card
Serial port for console