Question combination of some psu and mobo

[.valkyrie.]

hi. i had 3 psu and Mobo.... from gen 1 to 6....

i was going to use them once more. my question is , there are some information on PSU about 12-5-3.3 V that made me confused. i google that and people answered differently around forums.
for example, some said CPU use 3.3V and orher said it use 12V.

so here is what i found
12: CPu (maby) and GPu
5v: USB, HDD, and maby SSD and DVD drive.
3.3: ram and CPU (maby)

am i correct?


so basically if i want to have only a CPU (90w) +VgA (75w) + Ram 2x + HDD with NO other thing connected, then i need 14A from 12V ? i assume that ram and hdd use less than 10W and also its from other voltage..
so basically a 15-17 A from 12V reil can do the job? i am not talking about how efficient is this build . i just want to know if it do the job or not.

am i right or i am missing something?

 

[taeioum]

I think it will be easier to talk in hardware terms. Which components are we talking about? What motherboard/CPU/RAM/PSU do you have currently and which parts are you planning to upgrade?

If you want to calculate how much your new hardware will need in terms of wattage, try this website: https://outervision.com/power-supply-calculator

 

[.valkyrie.]

I think it will be easier to talk in hardware terms. Which components are we talking about? What motherboard/CPU/RAM/PSU do you have currently and which parts are you planning to upgrade?

If you want to calculate how much your new hardware will need in terms of wattage, try this website: https://outervision.com/power-supply-calculator

my question is about understanding those different reils. yea i haved used the calculator

 

[taeioum]

Hmm. Little calculation then, as RAM isn't on the 12V rail. CPU is on the 12V rail btw, you got that right.

90W + 75W + 12W (HDD use 12V 1A) = 177W / 12V = 14.75A. Of course you don't want to deliver exactly what is asked/required, so I'd definitely get a couple more Amps on the 12V rail just in case.

 

[geofelt]

At one time, processors did use 3.3 and 5v for most of their power.
Today, 12v is used for the cpu and gpu.
So, both answers were correct but incomplete.
Very old power supplies delivered most of their wattage at 3.3 and 5.v.
Today, it is mostly on 12v.

As a practical matter one does not need to know about those things.
The power required these days is mostly determined by the graphics cards.
Here is a handy chart:
http://www.realhardtechx.com/index_archivos/Page362.htm

Since a psu will only use the power demanded of it, regardless of the max capability, over provisioning is not a bad thing.

 

[.valkyrie.]

At one time, processors did use 3.3 and 5v for most of their power.
Today, 12v is used for the cpu and gpu.
So, both answers were correct but incomplete.
Very old power supplies delivered most of their wattage at 3.3 and 5.v.
Today, it is mostly on 12v.

As a practical matter one does not need to know about those things.
The power required these days is mostly determined by the graphics cards.
Here is a handy chart:
http://www.realhardtechx.com/index_archivos/Page362.htm

Since a psu will only use the power demanded of it, regardless of the max capability, over provisioning is not a bad thing.

so i think generation after lga 1155 considered 12V cpu...

these days, what devices will use 3.3 or 5v? and
so that i calculate how much Amper i need for that?
i am using Corsair cx650m for my personal build and its fine. but i want to understand it....


by the way , one of these old PSUs is Queen qu330qu.... with 2x 12V (double reil) each 12 Amp. total 200w

is that ok to use it on the system i mentioned above? whats writen on the box is (5v 20A) (3.3 20A) but rotal 100W...
and another total is 330W



another PSU , mazerati (3.3-28A) (5v35A) (12V25a) yea i know these old PSU brand are junk , at least 2nd one , because first one look genuine, but i am going to chose between them

 

[.valkyrie.]

Hmm. Little calculation then, as RAM isn't on the 12V rail. CPU is on the 12V rail btw, you got that right.

90W + 75W + 12W (HDD use 12V 1A) = 177W / 12V = 14.75A. Of course you don't want to deliver exactly what is asked/required, so I'd definitely get a couple more Amps on the 12V rail just in case.

So ram is 3.3? what devices will use 3.3 or 5v? so my list was not correct... i wonder why a psu need that much 3.3 or 5v Amp

 

[geofelt]

A psu with most of the amperage on 3.3 and 5v is old and really not suitable for a more modern processor.
If you MUST use one, plan on using integrated graphics.
Or, at most a discrete card like the gt1030 that only uses 30w.
A junky psu that is overloaded can destroy whatever it is connected to.

 

[.valkyrie.]

A psu with most of the amperage on 3.3 and 5v is old and really not suitable for a more modern processor.
If you MUST use one, plan on using integrated graphics.
Or, at most a discrete card like the gt1030 that only uses 30w.
A junky psu that is overloaded can destroy whatever it is connected to.

1- so basically 3.3 and 5V have no role in the modern build and they are completely useless? it seems everything use 12V so far... i'm not talking about this old build , but i would like to know how much Amper from those Voltage ⚡ do we actually need on a Modern PC.

2- also does having two reils of 12V make it bad?
i never had a two reil PSU, i wonder if its only different
inside of PSU
or
cable managements are also different and for example, i should connect one from V1 to for example Cpu and motherboard and V2 to GPU

 

[geofelt]

3.3 and 5v are still needed; they just do not need high amperage.

Most power supplies generate power from just one source.
They are divided into rails for safety reasons.

A psu will have only one 24 pin connector for the motherboard.
No choice there.

If a gpu needs two 8 pin connectors, it is best to use two separate leads from the psu.

Do not use one cable with two 8 or 6+8 pin connections to simplify cable management.

Two full 8 pin demands might overwhelm the single cable.