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What is the motivation of intel to want PSUs that are 12V only?
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tom66:
SMPSes are more efficient when designed for one output voltage, ideally with a load that is relatively close to the rating of the power supply. 

Having multiple rails complicates efficient design, because you need to handle crossload conditions and regulation across all rails. Many modern power supplies now use post-DCDC conversion, generating the -12V, 5V and 3V3 rails from the +12V supply, which eliminates the crossload issue. But as others have stated, this then needs to be distributed to the motherboard over lossy cables.  Why not just distribute it from the motherboard? The majority of high-power consumers are located there.

I wouldn't be surprised to see if the next SATA spec completely omits +12V from the power supply and drives run purely on +5V and/or +3V3 to reduce wiring harness size.

Another side benefit is, if the ATX spec allows it, the 12V rail might be able to go as high as 13.8V for a float-charged lead-acid battery.  I believe that's the technology Google use for some of their custom-built servers: each server has its own backup battery, instead of relying upon a larger UPS/generator with double-conversion.
madires:
The ATX specifiaction states ±5% for the 12V rail.
tunk:
I just opened a 5 year old Dell all-in-one PC and the PSU only had 12V.
tom66:

--- Quote from: madires on March 09, 2020, 05:15:27 pm ---The ATX specifiaction states ±5% for the 12V rail.

--- End quote ---

Was referring to the possibility of a modified or relaxed ATX spec with a 12V range of 11.5V ~ 14.4V.  I've found that at least one motherboard will operate on a relatively wide range of operating voltages but a HDD might not, as it began overspeeding and shut down (I modified an old ATX power supply on a Dell PC of mine to have an adjustable 12V rail out of interest, though this was many years ago.)
Psi:

--- Quote from: SiliconWizard on March 09, 2020, 02:08:24 pm ---

--- Quote from: Psi on March 09, 2020, 11:37:03 am ---And it would be super cool if they had the spec allow a voltage range that matched up to a number of lipo cells between flat and charged.

--- End quote ---

I'm not sure what purpose there would really be, I think they are mostly targetting desktop computer. Why would you want to power them with LiPo batteries?

--- End quote ---

It would be much more efficient/cheaper/simpler to connect batteries to the input of the motherboard than use a 110/220v inverter.
Imagine if you could simply add 3x high current Li-on 18650 cells in your computer case for a simple 1-2 minute UPS so you can save your work.
Monitor would need some sort of backup power too though, no point in pc running if you can't see anything :)
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