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geekhack Community => Other Geeky Stuff => Topic started by: suicidal_orange on Sat, 19 November 2016, 09:07:52

Title: Is -5v in a computer PSU still used?
Post by: suicidal_orange on Sat, 19 November 2016, 09:07:52
Carrying on from yesterday's hard drive fun I have filled every phone, memory card and old hard drive in the house with files, got most of them.  The computer crashed overnight while zero filling so there is a problem.

Found a PSU tester and all the lights are green except -5v, which of course is impossible to google anything about!  Anyone know if this is still used?  It's always been pathetic so might have been phased out, I hope.
Title: Re: Is -5v in a computer PSU still used?
Post by: nugglets on Sat, 19 November 2016, 10:43:57
https://www.lifewire.com/atx-24-pin-12v-power-supply-pinout-2624578

Only used in 20pin atx connectors, but still supported on some modern PSUs to maintain compatibility with older hardware.

edit - Pinout comparison: (http://www.smps.us/atx-pinout.png)

Title: Re: Is -5v in a computer PSU still used?
Post by: suicidal_orange on Sat, 19 November 2016, 10:51:49
Thanks, didn't think of looking for a pinout :thumb:

I don't really want to spend money on a new PSU only to wait until Tuesday for it to be delivered then find it doesn't help - life was so much easier when you could just swap parts with a friend but the world's gone laptop mad...
Title: Re: Is -5v in a computer PSU still used?
Post by: nugglets on Sat, 19 November 2016, 10:58:08
I know that feeling... Thankfully I have a graveyard of parts in the garage for these occassions.. or so I tell myself. The reality is I'm mostly just too lazy to lug it all to the recycler.

That said, I remembered learning about the -5v change from 20 to 24 pin but couldn't remember what it was actually used for. Because I know you can use a 24pin connecter in a 20pin mobo without issues these days, it got me wondering. Just looked it up and it was only used for ISA bus... so it has been obsolete for a very, very long time.

Not that any of this information really helps you, but the more you know right? =)

Good luck!
Title: Re: Is -5v in a computer PSU still used?
Post by: suicidal_orange on Sat, 19 November 2016, 11:08:02
Haha, ISA... that was a while ago.

My parts bin is useless as this is only my second 24pin PSU and the first I gifted to a friend when he bought a mobo, CPU and RAM because I suspected it was dodgy, but he ran it for a couple of years before it died.  Then he got a laptop.

I'm waiting for a crash with a drive related sound, 8.33 hours to fill a slow and quiet 3tb drive so I think caffeine would be more useful than luck but thanks anyway!
Title: Re: Is -5v in a computer PSU still used?
Post by: soilheart on Sat, 19 November 2016, 14:19:06
Oh, I replaced a PSU without a -5v pin with a new one with a -5v pin the other week (had to look it up what the extra pin was to make sure that it wouldn't cause any issues ;) ).

I assumed it was used by serial bus:es, but I just realized that (the actual) RS232 standard calls for 12v to -12v... and that pin is still around so clearly my assumption was wrong.

On a related note, my father used an ISA soundcard for a long time, as he found it much better than the built-in ones. I think he finally had to give it up when he bought a new computer a year ago (which have no extra extension card slots whatsoever =P).
Title: Re: Is -5v in a computer PSU still used?
Post by: suicidal_orange on Sat, 19 November 2016, 19:43:53
9.5 hours into my theoretical 8.33, some strange messages about USB but still seems to be writing to the dodgy drive, if I weren't soaked with rain I'd call it a night but soggy hair doesn't make for a good sleep...

PCI soundcards have been around for many years and surely there are PCI-E ones these days - I agree there are improvements over onboard, I've used a USB DAC for years :)
Title: Re: Is -5v in a computer PSU still used?
Post by: 0100010 on Sat, 26 November 2016, 22:59:24
I've got a "benchtop power supply" made from an old ATX PSU and adapter board, but not old enough that it still supplied -5VDC, so that location on the board doesn't have a post mounted.