How many wattage of power supply do i need ? with these componenets

[Baba Yaga]

rx7800xt + ryzen 9 7900x..

[Hinjima]

12 minutes ago, Baba Yaga said:

rx7800xt + ryzen 9 7900x..

A quality 750 or 850w will be plenty

7800XT Max power draw is 263w and 7900x maxes out at 170-230w depending on motherboard settings.

[PDifolco]

Needs 500W at full max load, a good 650W will more than be enough, or get a 750W for some more headroom

[8tg]

So here’s how you do this math even without pcpartpicker doing it for you, since apparently you just want other people to google things for you.

 

Look up the 7800xt and scroll down to its specs page:

https://www.amd.com/en/products/graphics/amd-radeon-rx-7800-xt

now that’s pretty generalized, that’s amds reference card spec. You can also get this same information from techpowerup which has an entire database of gpu specs.

If you’re getting a specific aib variant you can check what they list as well, factory overlocks increase power consumption.

 

Do the same with the cpu

https://www.amd.com/en/products/cpu/amd-ryzen-9-7900x

Now tdp isn’t actually wattage but its close enough, am5 as a socket can actually tap 230 watts of real power delivery by spec, and most factory speed higher end CPU’s will be somewhere below that. You can find that out by looking up “cpu name power draw” and there’s usually a bunch of reviews on most mainstream CPU’s that shows power from the wall metrics. 
 

So now with those two components, we have 433 watts of potential draw under peak synthetic load at stock speeds. And that’s just the two core components. The other stuff is either negligible or has rough coverall estimations. For example your ram power draw is unimportant, as are fans or coolers unless you have a massive amount of fans. Custom water cooling sometimes you need to take that stuff into consideration but if you’re doing that, you’re not asking about power draw, because you probably already know.

The motherboard itself it’s generally considered as 50 watts for average boards, 100 watts for enthusiast boards with high end chipsets. So we’ll just tack 100 watts on to cover that idea.

533 watts under full synthetic load. Cool, so a 600w psu? Absolutely not. 
 

Power supplies are named by their peak short burst output. A 600w psu is rated to hit 600 watts for maybe a second or two. It can sustain usually 100 watts less, for most modern power supplies anyway. Which is why when people are calculating power draw, you see psus recommended usually 150-200 watts higher than needed. To accommodate for extended full system load. 
So accounting for that you want basically a 700-750 watt power supply for your 430w core power draw estimate. 
Note everything is an overestimate, power supplies have a pretty wide efficiency range so being a bit over is not a concern. You don’t want to scrape by with the bare minimum you need.

You may also want to go over for room for overclocking your hardware, or potential higher power draw items in the future. The 7800xt is fairly power efficient for its tier of gpu, but lets say in a year you find a good deal on an rtx 4090, now your power draw under load goes from 263 watts to 400 or more for higher end models. And your 750w psu is no longer suitable, it’s the bare minimum. Keep longevity in mind.

[Bagzie]

On 12/30/2023 at 10:11 PM, 8tg said:

So here’s how you do this math even without pcpartpicker doing it for you, since apparently you just want other people to google things for you.

 

Look up the 7800xt and scroll down to its specs page:

https://www.amd.com/en/products/graphics/amd-radeon-rx-7800-xt

now that’s pretty generalized, that’s amds reference card spec. You can also get this same information from techpowerup which has an entire database of gpu specs.

If you’re getting a specific aib variant you can check what they list as well, factory overlocks increase power consumption.

 

Do the same with the cpu

https://www.amd.com/en/products/cpu/amd-ryzen-9-7900x

Now tdp isn’t actually wattage but its close enough, am5 as a socket can actually tap 230 watts of real power delivery by spec, and most factory speed higher end CPU’s will be somewhere below that. You can find that out by looking up “cpu name power draw” and there’s usually a bunch of reviews on most mainstream CPU’s that shows power from the wall metrics. 
 

So now with those two components, we have 433 watts of potential draw under peak synthetic load at stock speeds. And that’s just the two core components. The other stuff is either negligible or has rough coverall estimations. For example your ram power draw is unimportant, as are fans or coolers unless you have a massive amount of fans. Custom water cooling sometimes you need to take that stuff into consideration but if you’re doing that, you’re not asking about power draw, because you probably already know.

The motherboard itself it’s generally considered as 50 watts for average boards, 100 watts for enthusiast boards with high end chipsets. So we’ll just tack 100 watts on to cover that idea.

533 watts under full synthetic load. Cool, so a 600w psu? Absolutely not. 
 

Power supplies are named by their peak short burst output. A 600w psu is rated to hit 600 watts for maybe a second or two. It can sustain usually 100 watts less, for most modern power supplies anyway. Which is why when people are calculating power draw, you see psus recommended usually 150-200 watts higher than needed. To accommodate for extended full system load. 
So accounting for that you want basically a 700-750 watt power supply for your 430w core power draw estimate. 
Note everything is an overestimate, power supplies have a pretty wide efficiency range so being a bit over is not a concern. You don’t want to scrape by with the bare minimum you need.

You may also want to go over for room for overclocking your hardware, or potential higher power draw items in the future. The 7800xt is fairly power efficient for its tier of gpu, but lets say in a year you find a good deal on an rtx 4090, now your power draw under load goes from 263 watts to 400 or more for higher end models. And your 750w psu is no longer suitable, it’s the bare minimum. Keep longevity in mind.

 

 

Power supplies are rated at there max sustained rate , Transient spikes are a part of ATX 3.0 spec and are actually rated for short bursts well beyond there rated wattage.

 

Some can sustain more than that , For example my PSU is rated at 750w because it is also rated as platinum efficiency , In testing it will hold a sustained 850w just fine but that would bring its rating down to gold so they rated it at 750w.

 

As per the atx spec.

 

Rated for up to 200% of rated power for 100μs (with a 10% duty cycle), That's actually much longer and much more time spent above rated spec than any transient loads will give.

 

I have no problem with you suggesting a very high wattage psu if the OP is planning a 4090 and 14900k in the future but with your logic everyone should buy a 1000w psu just incase which is nuts.

 

The OP gave no indication he wants a 4090 in the near future so why jump to extreme scenarios for no reason.