The Sun Fire T1000 is one of very few servers that has an open source CPU. The CPU in this server is the Sun UltraSPARC T1. This is a SPARC V9 CPU with a maximum of 8 cores and 32 threads running at 1.4Ghz. This was a new design for Sun, one that originated at another company which Sun bought. This CPU and the followup, the T2, are unique in that Sun released the Verilog sourcecode for the CPU. The server itself is a neat looking 1U model.
The server suffers one big issue that most 1U servers have. Noise. The tiny fans in the server have 1 setting, jet engine. Combined, the server fans consume more power then the CPU! As this CPU is from 2005, the impressive 32 threads have gotten a lot less impressive. A single core from a modern Ryzen CPU beats it, but that is of course not too surprising. Installing an OS on this is also "fun". It can only netboot as it just has Ethernet ports!
I installed a few resistors the lower the voltage to the fans in an attempt to make it less loud. But even with this the server was just too noisy to use at home. After it collecting dust for a while it got sold to someone who has a nice basement rack so sound is no issue.