I've got a FreePBX 2.8 server (yes, 11 years old) that's been running my home phones for the last decade+. It runs CentOS 5.5, on a fanless Intel Atom CPU with 1GB of RAM.<p>I've hacked on it quite a bit, customizing some bits here and there. Learned a lot about SIP, UDP, Asterisk, a bit of PHP, Linux, apache, etc over the years. Been a lot of fun! Along the way at some point I swapped an SSD in to make it fully solid state.<p>I know one day I should "upgrade" it but the damn thing is so reliable. It will probably outlive me if I had to wager.