I keep coming across things like this eBay listing. Sun Enterprise 4500, 12 SPARC processors (400 MHz, 4MB cache) and 12 GB of RAM. This one looks to have a couple Gigabit fiber NICs, too. (Although it’s fiber, so you’d need a pricier switch to use it on a “normal” copper home LAN.)
Even if you foolishly assume that a 400 MHz SPARC is no better than a 400 MHz Celeron, with 12 processors, this is still a net of 4.8 GHz. With a dozen processors, this is clearly best for something that’s very multi-threaded.
Of course, there’s one problem: these machines use SCSI disks. SCSI’s great and all, but it’s expensive, and you can be sure that, if this machine even comes with hard drives (none are listed?), they’re 9GB. So pick up one of these. What’s that you say? Oh, it’s ATA and won’t work with SCSI? No problem!
Nowhere that I see does Sun mention whether Solaris 10 / OpenSolaris will run on older hardware, but I assume it will. Some Linux distros also excel at running on platforms like SPARC.
Now the real question: how much electricity does this thing use?