possibly off-topic: SGI (was Rackable) sells an entire line of DC servers. I've got *cough* *cough* a lot of them. It's any AC power that you can name (240, or 3phase, or 120) coming into the cabinet, through the rectifiers and into DC bussbars. All the servers run off that clean DC power. If you are in a DC-capable datacenter, just get them to drop the 300A "lugs" straight to the cab and skip the rectifiers.
The rectification system in 95-97+% efficient, at all loads, which is much better than most AC switching power supplies. If you take a 450W power supply and only draw 200W, it's rather inefficient. Since that 450W (or 600W) supply is there in case you put in all the RAM, and all the drives, and the fastest CPU, and most people don't... you get the idea. (This is why HP and some other blade chassis actually shut down extra power supplies when the internal load is low, it is better to run fewer supplies are closer to 90-100% of their max, than to run more supplies at 20-30% of the rated loads.) --tep ps If you want the history on why it's -48V DC, check out the archives of the "Telecom Digest" where lots and lots of Bell folks hung around to talk to hobbyists and fans. I'm sure it's in there somewhere :-) _______________________________________________ Tech mailing list [email protected] https://lists.lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
