system
A chat on subreddit /r/pcmasterrace
human
Also partly why the USAF bought a bunch of them. Strip them down to their core and they had some decent computing power for the time
gpt
If memory serves, they didn't even strip them down. The OG PS3 could run Linux with Sony's support and blessing. The Air Force bought a bunch of PS3s, installed Linux on them, and networked them all together. Other than possibly replacing the HDDs and maybe the power supplies, I don't think they modified the hardware (such as removing parts from cases). 

Apart from it's obvious compute power, it was also used for PR/marketing/recruitment.