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What is the motivation of intel to want PSUs that are 12V only?
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OwO:
12V is still way too low. A 500W system would draw 42A, which is difficult to transport and requires huge connectors with many pins. 48V is more reasonable; the motherboard can then step it down to 12V and then to the individual voltages. DC-DC conversion stages are never a problem; I use single rail supply even for small modules (e.g. FPGA board + daughterboards), and always generate all rails locally.

EDIT: pretty sure google uses 48V at the server level and something like 400V DC at the rack level.

Personally I would go with 70V. It's the highest I can still comfortably touch and at this level the higher the better. The DC-DC converter on the motherboard doesn't have to be transformerless.
SiliconWizard:

--- Quote from: OwO on March 05, 2020, 04:19:06 pm ---12V is still way too low. A 500W system would draw 42A, which is difficult to transport and requires huge connectors with many pins. 48V is more reasonable; the motherboard can then step it down to 12V and then to the individual voltages. DC-DC conversion stages are never a problem; I use single rail supply even for small modules (e.g. FPGA board + daughterboards), and always generate all rails locally.
(...)

--- End quote ---

12V is part of the legacy I think, but there's another reason IMO. The idea of down-converting voltages more locally is generally a good one. But 12V is likely close to the sweet spot for the following reason: step-down converter ICs that operate with higher input voltages than this are just going to be much more expensive, as this gets into the "high-voltage" territory for current CMOS processes. 48V or over would make local step-down converting much more expensive. You could say that you can always chain them to overcome this, but then you have a chain of efficiencies which would make efficiency for the low voltages (which currently draw the most current on computer motherboards) pretty poor. Just a thought.
Gregg:
Single 12VDC would certainly make sense for a UPS type system; no inverter needed.   :-+
Red Squirrel:
Would be cool if they made it 13.5v actually, would make power backup simpler, just needed a battery set to float voltage.   Currently, PCs have lot of power rails so doing a straight DC type backup would be too complex.   3.3v, 5v, 12v, -12v... I feel I'm missing one. Is there a -5v?

Really a 48v/54v standard would be cool.   That's how telecom gear works.
ve7xen:

--- Quote from: CJay on March 05, 2020, 05:00:58 pm ---
--- Quote from: OwO on March 05, 2020, 04:19:06 pm ---12V is still way too low. A 500W system would draw 42A, which is difficult to transport and requires huge connectors with many pins. 48V is more reasonable; the motherboard can then step it down to 12V and then to the individual voltages. DC-DC conversion stages are never a problem; I use single rail supply even for small modules (e.g. FPGA board + daughterboards), and always generate all rails locally.

EDIT: pretty sure google uses 48V at the server level and something like 400V DC at the rack level.

--- End quote ---

48V is the standard at the bladecentre level, many enterprise level servers will have an option for a redundant 48V-12V DC-DC converter instead of a line voltage AC-DC 12V PSU

The 12V only desktops I see have a really short, multiconductor PSU tail but I don't see much brand variety so that may not be typical

--- End quote ---

-48VDC is even more legacy than the 12V rail in ATX. It goes back to telco central office standards and their lead-acid battery plants, probably predates home computers entirely. Still common in telecom to have -48VDC as the main power distribution, so most gear you might find in a telco facility (networking, servers, etc.) will have a PSU option for that. It does make a lot of sense from a high reliability point of view, it's a simple design and easy to scale, but it also probably wouldn't be the choice if you were in a completely green field today.
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