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  #1  
Old 08-10-2018
Oliver Valdéz Guzmán Oliver Valdéz Guzmán is offline
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Default only 12V maximum capacity is important right?

Do minor rail ratings (like 5, 3.3, -12V) matter?

Or it is almost impossible to overload those rails these days?

If they DO matter, in which cases they would need to be considered?
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Old 08-10-2018
COFASA COFASA is offline
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I'd say no

since the most power hungry components are the CPU and GPU, and those are 12V mostly

I don't think you would be limited by the other rails, if the PSU has enough 12V output for your parts you can almost take for granted that you have enough power on the other rails as well.

I could be wrong though
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Old 08-10-2018
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5v capacity can be limiting if you have a ton of storage or high powered USB devices. 3.3v is negligible at best these days as it generally only powers some board ICs as well as some PCIe stuff.

-12v is completely irrelevant and not used today.
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Old 08-10-2018
Oliver Valdéz Guzmán Oliver Valdéz Guzmán is offline
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Quote:
Originally Posted by Tator Tot View Post
5v capacity can be limiting if you have a ton of storage or high powered USB devices. 3.3v is negligible at best these days as it generally only powers some board ICs as well as some PCIe stuff.

-12v is completely irrelevant and not used today.
Thank you so much, so there are instances where 5V does matter but they won't affect most users is that right?

You should look at 12V only

and what's the point of -12V? retrocompatibility?
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Old 08-10-2018
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Quote:
Originally Posted by Oliver Valdéz Guzmán View Post
Thank you so much, so there are instances where 5V does matter but they won't affect most users is that right?

You should look at 12V only

and what's the point of -12V? retrocompatibility?
Yeah, old (very old) PCI / Serial connections used -12v in the past, but most of that hardware was outdated in 2003. Unfortunately Intel built the ATX 2.x standard to be backwards compatible so we retained the -12v.



The -5 was used by Dynamic RAM in the past, but with the move to SD-RAM (what we use now) this has become obsolete. It was also used on the ISA bus but that was obsolete by the time of ATX 1.3 which is why it and -5v were dropped from ATX 2.0 standard.



5v, like I said, matters most when you have a ton of hard drives. Then on modern systems, especially with units that only have 100-120w on the 5v/3.3v combined rail, you can run into issues. For most users though, it's not a concern as they'll have at max, 3 drives.
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Old 08-11-2018
Stefan Payne Stefan Payne is offline
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Quote:
Originally Posted by Oliver Valdéz Guzmán View Post
Do minor rail ratings (like 5, 3.3, -12V) matter?
If its 7-10A or more, no its enough and no problem at all.

Quote:
Originally Posted by Oliver Valdéz Guzmán View Post
Or it is almost impossible to overload those rails these days?
Pretty much.
At least its very hard as almost nothing uses the +5V Rail.
The only things that still use +5V are drives. And you need a whole bunch of drives to get close...


Quote:
Originally Posted by Oliver Valdéz Guzmán View Post
If they DO matter, in which cases they would need to be considered?
Getting the K7 system out of the basement and using that.

Besides that, I can't think of much as most things that even consume +5V don't consume that much...
And even then, there usually is a voltage regulator before that (on the Motherboard)...

Thing is:
If the ATX connector had more +12V Connectors, nobody would use the +5V Rail...

So we need a new specification...
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