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Old 09 February 2014, 03:48   #1128
Mr B
Registered User
Join Date: Nov 2005
Location: Sweden
Posts: 746
Originally Posted by Loedown View Post
Some modern ATX supplies aren't even coming out with a -5 V rail any more which means a 7905 needs to be connected to the adapter cable with a couple of capacitors.
Some? With ATX 1.2 it was "optional" but ever since ATX 1.3 became the standard, -5v is no longer a part of the specification. It's not explicitly prohibited, but since it was only included for legacy (ISA) systems to start with, and ATX standard 1.3 is over 12 years old... No wonder -5v is rare on the ATX PSU these days. Luck, or just planing, has it that a lot of cheap, low watt PSU's still have the -5v we need where as it's more uncomon on enthusiast, high watt PSU. I'm guessing, but it might just be an artifact of old designs that means the -5v is available, so they provide it, it can also be intentional, knowing that if someone has a older ISA system, and needs a replacement PSU, they aren't going to need a high watt unit, but will go with a low one.

For a real answer i guess someone should ask FSP or someone... As far as i know, FSP have excluded -5v from all their branded PSU's, but still provides OEM PSU's with -5v available, if they ask for it. Seasonic did to, not sure about now?
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