According to PSU calculator not enough 3.3V and 5V power?

[Grayblade]

Hi! I used outervision.com to calculate if my PSU could handle RTX3080 and other upgrades.

 

My current system is:

PSU: 660W Fractal Design ION+ 660

MB: ASUS ROG STRIX B450-F GAMING

CPU: Ryzen 5 3600 /w PBO on

COOLER: CM Hyper 212 RGB Black Edition

RAM: Corsair 2x 8GB 3200MHz CL16

DRIVES: NVMe Sams. 970 EVO Plus 512GB and HDD WD Green 2TB

GPU: GT 710

Monitor: 1440p LG 27GL850

 

Using PSU calculator I added upgrades that I would be interested: https://outervision.com/b/wYIbLs

CPU to 5600x and GPU to RTX 3080.

Then fully populate ram slots (4x), add another NVMe (3 drives total), set gaming keyboard and mouse.

Add 4x UBS 3.0 devices just incase I have lot of devices plugged in.

 

I get this result:

+3.3V - 13.8 A and +5V - 13.3 A    
Total 113 W

+12V - 38.6 A
Total 463 W

Combined 525 W that should be plenty of power for the system.

 

However my PSU can output 110W for 3.3V and 5V and 660W for 12V (info from the box).

Now I'm concerned that I don't have enough PSU for 3.3V and 5V.

This that a thing? Should I be concerned? So far I knew not enough 12V was main concern.

[Guest]

The Outervision calculator is bull shit.

 

[mariushm]

That calculator does the math assuming that the nvme drives are powered directly from the 3.3v output of the power supply.

That's not the always the case, there's often if not always a DC-DC converter which converts either 12v or 5v from power supply to 3.3v which is used by m.2 drives. 

 

A nvme SSD will use up to 10 watts ( 3.3v at 3A) when writing a lot of data but again, the M.2 connectors are probably not powered directly from the power supply's 3.3v output, so don't just put there  3 x 3A = 9A on 3.3v 

 

Each stick of RAM uses maybe 6-8 watts, and since they run at 1.2v..1.35v this voltage is generated on the motherboard using a dc-dc converter that converts 12v or 5v to that lower voltage. I think rarely 3.3v is used.  So let's say ~ 8 watts x 4 sticks = 30 watts ...

If it's converted from 5v, then that's 6.5A or so taken from 5v 

 

The motherboard (chipset, onboard audio, network etc) will use around 10-20 watts, mostly from 5v stand-by and 5v. 

 

Your CPU will average around 80 watts, all from 12v output of your psu. For simplicity, round it up to 100 watts. 

The fans use 2-3 watts all from 12v - you can look on the label and you'll see something like 12v 0.15A   ... multiply them and you get the watts. 

The  GT 710 uses ... jesus, I don't know, it's a shit video card, maybe 30-50 watts from 12v output of your power supply?

 

A 3080 will use maybe 250-300 watts, all from 12v output of your power supply. 

 

[Somerandomtechyboi]

10 minutes ago, jonnyGURU said:

The Outervision calculator is bull shit.

 

Yep

 

When i was a complete noob i used it but that was before i even built a computer or still on my first computer

 

And later on realised that psu calculators are full of shit

 

 

Tbh you will want to look at the rails for accurate psu requirements not just a vague "696w"

 

So if a 696w psu has 420w on the 3.3v and 5v combined and 276w on the 12v, it wont be able to power something like an rtx 3060

[Master Disaster]

Also 3080s/3090s are known for "high transient loading" or AKA sudden power spikes. Apparently 3090s can quickly jump up to 800w on their own for very short bursts. While this isn't likely to damage the PSU it does cause overcurrent protection to trip if the PSU isn't rated high enough to cope.

[Grayblade]

1 hour ago, jonnyGURU said:

The Outervision calculator is bull shit.

 

What would you suggest I use to calculate if my PSU can handle the system?

Are there better PSU calculators or avoid all of them?

 

55 minutes ago, Somerandomtechyboi said:

Yep

 

When i was a complete noob i used it but that was before i even built a computer or still on my first computer

 

And later on realised that psu calculators are full of shit

 

 

Tbh you will want to look at the rails for accurate psu requirements not just a vague "696w"

 

So if a 696w psu has 420w on the 3.3v and 5v combined and 276w on the 12v, it wont be able to power something like an rtx 3060

 

This is what I got:

 

 

12V looks good enough? According to Guru3D review PSU can handle up to 700W of load.

 

[Grayblade]

1 hour ago, mariushm said:

That calculator does the math assuming that the nvme drives are powered directly from the 3.3v output of the power supply.

That's not the always the case, there's often if not always a DC-DC converter which converts either 12v or 5v from power supply to 3.3v which is used by m.2 drives. 

 

A nvme SSD will use up to 10 watts ( 3.3v at 3A) when writing a lot of data but again, the M.2 connectors are probably not powered directly from the power supply's 3.3v output, so don't just put there  3 x 3A = 9A on 3.3v 

 

Each stick of RAM uses maybe 6-8 watts, and since they run at 1.2v..1.35v this voltage is generated on the motherboard using a dc-dc converter that converts 12v or 5v to that lower voltage. I think rarely 3.3v is used.  So let's say ~ 8 watts x 4 sticks = 30 watts ...

If it's converted from 5v, then that's 6.5A or so taken from 5v 

 

The motherboard (chipset, onboard audio, network etc) will use around 10-20 watts, mostly from 5v stand-by and 5v. 

 

Your CPU will average around 80 watts, all from 12v output of your psu. For simplicity, round it up to 100 watts. 

The fans use 2-3 watts all from 12v - you can look on the label and you'll see something like 12v 0.15A   ... multiply them and you get the watts. 

The  GT 710 uses ... jesus, I don't know, it's a shit video card, maybe 30-50 watts from 12v output of your power supply?

 

A 3080 will use maybe 250-300 watts, all from 12v output of your power supply. 

 

 

I was using PSU calculator to get some estimation but it looks more complex now.

Thanks for taking time to explain. Learned new things about PSU.

 

[Elisis]

7 minutes ago, Grayblade said:

What would you suggest I use to calculate if my PSU can handle the system?

Maybe some simple addition based on reviews on the relevant parts?

[mariushm]

You'll be fine. 

Your power supply can supply up to 660 watts on 12v.

It can also supply up to 66w on 3.3v  and up to 100w on 5v, but not both at the same time.. the total budget for them combined is 110w. So if your components use 20A on 3.3v, then you're left with a budget of  110w - 66w = 44w on 5v ... that's how you read it. 

 

The 3.3v output on power supplies is not really used a lot, motherboard makers don't rely on it.. If there's something that uses lots of power on 3.3v (ex m.2 connectors) it's more convenient to add a dc-dc converter on the motherboard and produce 3.3v from 12v or 5v. 

 

The 5v is more important, as it's also used by USB ports.

[Grayblade]

32 minutes ago, Master Disaster said:

Also 3080s/3090s are known for "high transient loading" or AKA sudden power spikes. Apparently 3090s can quickly jump up to 800w on their own for very short bursts. While this isn't likely to damage the PSU it does cause overcurrent protection to trip if the PSU isn't rated high enough to cope.

I've read about big power spikes too. RTX 3080 could go up to 500W, however  haven't found info what cards do that.

I'm looking to get entry level RTX 3080 like a Eagle/Ventus/TUF (when there is stock) that consume little bit less power and healthy undervolt to tame the wattage.

[Grayblade]

15 minutes ago, mariushm said:

You'll be fine. 

Your power supply can supply up to 660 watts on 12v.

It can also supply up to 66w on 3.3v  and up to 100w on 5v, but not both at the same time.. the total budget for them combined is 110w. So if your components use 20A on 3.3v, then you're left with a budget of  110w - 66w = 44w on 5v ... that's how you read it. 

 

The 3.3v output on power supplies is not really used a lot, motherboard makers don't rely on it.. If there's something that uses lots of power on 3.3v (ex m.2 connectors) it's more convenient to add a dc-dc converter on the motherboard and produce 3.3v from 12v or 5v. 

 

The 5v is more important, as it's also used by USB ports.

That eased my mind. Thanks again for PSU tips!