# Why does the mother board actually use?

Discussion in 'Power Supplies' started by ecktt, Jun 18, 2015.

1. ### eckttLimp Gawd

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So the CPU and RAM runs on 2V or less. Why not use the 3.3V line? What does the 12V, 3.3V and 5V lin actually power in a modern PC? Does the USB even use the 5V line? What about the -12 or -5?

2. ### drescherjm[H]ardForum Junkie

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One reason is the current would be much higher on the 3.3V line requiring very thick wires or many more.

The USB port supplies +5V so its safe to say yes.

3. ### jojo69[H]ardForum Junkie

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you want welding cables going to your mobo...lol?

W=VxA

4. ### Zepher[H]ipster Replacement

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wouldn't it be less current with more volts?
let's say the cpu is 95watts.
if we ran 95 volts to it, it would only use 1 amp.
if we ran 1 volt to it, it would need 95 amps.

5. ### drescherjm[H]ardForum Junkie

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Exactly. The CPU gets its power from the +12V line. Using the 3.3V line for that would require larger conductors on the 3.3V line.

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precisely

7. ### Tsumi[H]ardForum Junkie

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Theoretically yes. The problem is that semiconductors can only work within a certain voltage range. Put too many volts in and you burn out the circuits regardless of amperage.

8. ### npublici[H]Lite

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Electrical power is a combination of current and voltage.If voltage is increased, less current is required.High voltage and low current requires conductors of smaller size.In the same way your household voltage is 120(in the US)while the power is supplied to near your home with voltages of 14 thousand volts or more on small wires.Motherboards use solid state devices to convert the 12volts low current to low voltage high current,after it has traveled across the motherboard at higher voltage on relatively small conductors.

9. ### eckttLimp Gawd

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So, it would be safe to assume the mother board uses Voltage regulators to step down the voltage?
Wouldn't that create a lot of heat? Why not use the 12V for everything?

I know, I'm being a pain but my PC Power and Cooling 750Watt is on its way out (random reboots/lockups). It lasted over 7 years and when it's replaced, I'd like to know I pick a replacement that will allow it to grow into a new system and last another 7 years.

10. ### AlienTechLimp Gawd

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Lower voltage levels means less heat and power usage. NAND chips use upto like 20 v, which is why they have different ones like SLC, MLC, TLC which store multiple bits.. You cant do that with like 3V.. A few decades ago they said we cant use less than 5V because transistors need that voltage for switching but lowering it to less than 1V now, uses far less power. It also means lower frequencies.. So its a fight between higher voltage and speed which is why during over clocking you pump in more voltage. At 12V that cpu would consume like 500 watts and the heat would be HIGH but you could also pump it to far higher speeds. This is very difficult as we see.. Intel can do some of this because their materials divisions from all the companies they bought also brought with them the technologies for doing it while AMD is all in house pretty much. Originally AMD had some nifty ideas and were much faster than Intel.. But once Intel got DEC and HP they just blew past the old transistor world into exotic materials. Some of those HP and DEC guys were decades ahead but they had nothing to show for it and in business its better to let someone else create it and then buy them out cheap when they are broke.

11. ### AlienTechLimp Gawd

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I highly doubt anything these days will last 7 years. it might but they just are not designed to last. Every component is designed to be specd for tolerences and to work a short period. It is all done on purpose and also cost. Saving cents here and there adds up to a few bucks overall.. It is nothing like a decade or two ago. I bet there are computers thats 20-30 years old still working. I doubt you will find a 2010 phone or laptop working in 2020 let alone 2030.

12. ### drescherjm[H]ardForum Junkie

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I do not expect a major change in the standard any time soon. You should be fine with a quality power supply. Look at the reviews here for ideas.

Although there is always a chance that you buy the best quality power supply (with the lowest failure rates) and unluckily it fails for you in a month.

Last edited: Jun 27, 2015
13. ### jojo69[H]ardForum Junkie

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I believe that quality PSUs will work for many decades with periodic replacement of electrolytic capacitors.

14. ### Tsumi[H]ardForum Junkie

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Yes, both the motherboard and GPU use VRMs to step down the voltage. Yes, it creates a lot of heat, but it creates far less heat than having your PSU supply 0.9-1.8 volts.

Semiconductors aren't designed to operate at 12 volts, physics and properties of silicon semiconductors come into play.