IPFire is very versatile and running on many different kinds of hardware. Those can be 19"-rack-mounted servers as well as small boxes that fit on the palm of a hand.
|Processor||x86 CPU with 1 GHz or better or a supported ARM SBC|
|Memory||1GB or greater|
|Storage||at least 4GB of harddisk storage|
|Network||at least two Ethernet network adapters|
Read more about System Requirements of IPFire.
A collection of articles explains which hardware features are desirable for IPFire and which hardware should be avoided to not risk any hardware failures or bad performance.
Basically any x86 based system (with AMD or Intel processor) works very well with IPFire. The ARM architecture however is not that compatible. Please check out which single board computers are supported and which not in the ARM hardware section.